Compiled from the Foundation for the Study of Cycles archive (Cycles Magazine, vols. 1950–1957)

A Note Before You Start

Unlike the Brunt entry, this one is thin by necessity — Playfair appears in the archive via a single reader's letter, plus one index reference to a reprinted chart. There's no article, no analysis by Dewey himself, no cycle lengths attributed to him. What makes him worth writing up isn't volume of material — it's that even the letter-writer flagged him as someone who'd been overlooked by cycles researchers who should have known his work.

How He Surfaces in the Archive

Playfair doesn't appear because the Foundation was studying him — he appears because a reader corrected the Foundation's blind spot. In the 1956 volume, a reader named Edward F. Moore of New York wrote in response to a piece on Sir Flinders Petrie's The Revolutions of Civilization (1911), which Dewey had reprinted and praised as pioneering work on long cultural cycles. Moore's letter reads, in substance:

He was especially interested in the piece on Petrie, but pointed out that the Foundation might not be familiar with an earlier writer who did similar work a full century before Petrie: William Playfair, who published in London in 1805 a book titled An Inquiry into the Permanent Causes of the Decline and Fall of Powerful and Wealthy Nations. Moore happened to own an original copy, and sent the Foundation a photostatic copy of the title page and Playfair's principal chart — which the Foundation then reprinted across two pages of the magazine.

That's the entirety of the biographical and bibliographic content on Playfair in the currently loaded volumes.

What This Tells You

A few things worth noting for your forum piece:

1. Playfair predates the field's own sense of its history. Even the Foundation for the Study of Cycles — an organization explicitly dedicated to cataloguing every prior instance of cyclic thinking across history — didn't know about Playfair until a reader pointed it out in the mid-1950s, nearly 150 years after Playfair's book was published.

2. The comparison to Petrie is the whole point. Dewey had praised Petrie's 1911 Revolutions of Civilization as an early, clear-eyed treatment of long civilizational cycles. Moore's letter is essentially saying: "You're a century too late crediting the right pioneer." Playfair's 1805 work covers the same conceptual ground — the rise and fall of powerful nations, illustrated graphically — but did it first.

3. Playfair's real historical significance is bigger than this letter suggests. Outside the cycles literature entirely, Playfair (1759–1823) is now generally credited as the inventor of several fundamental statistical chart types — the line graph, bar chart, and pie chart — making him a founding figure of data visualization itself, decades before these became standard tools. None of that appears in the archive; the Foundation's interest in him is narrowly about the "decline and fall" cyclic thesis, not his innovations in graphical statistics. This background is not sourced from Cycles Magazine — it comes from general historical knowledge and should be verified independently before you post it, but it may be worth including on your forum since it substantially raises Playfair's importance beyond what the magazine itself captured.

4. The reprinted chart itself is not captured in extractable text in the currently loaded volume — the index simply notes "Universal Commercial History, Chart of, by William Playfair," pages 176–77 of the 1956 volume. If you want the chart itself (which was apparently significant enough for the Foundation to reprint across two full pages), that would need a direct look at the page images rather than the text extraction, since charts don't survive OCR/text conversion.

Suggested Forum Angle

Given how little the Foundation itself said, the more interesting story for your readers may not be "what Playfair found" but "how a foundational figure gets lost even to the people whose entire job is remembering this stuff" — and how it took an ordinary reader with a private collection, not a professional cycles researcher, to correct the record.

An engineer's second career

Alexander "Sandy" Thom was born on 26 March 1894 in Carradale, Scotland, the son of a tenant farmer. He trained as an engineer at the University of Glasgow and went on to a genuinely distinguished technical career: during the Second World War he served as Principal Scientific Officer responsible for the design of the High Speed Wind Tunnel at the Royal Aircraft Establishment, Farnborough, and assisted Barnes Wallis with the aerodynamics of the famous "bouncing bomb" used in the Dambusters raid. He later became Professor of Engineering Science at Oxford, where the university's Thom Building is named after him.

Alongside this career, from around 1934 onward, Thom developed a private obsession that would eventually consume the rest of his life: the stone circles, standing stones, and stone rows scattered across Neolithic and Bronze Age Britain, Ireland, and Brittany. From roughly 1933 to 1977 he spent most of his weekends and holidays hauling a theodolite around the countryside, often accompanied by his son Archie, painstakingly surveying site after site to professional engineering standards — a level of measurement precision archaeology had rarely if ever applied to these monuments before. He retired from academia in 1961 specifically to devote himself full-time to the work. By the end, he and his family had surveyed over 500 megalithic sites.

The megalithic yard

Thom's first major claim, published in a 1955 paper and developed at length in his 1967 book Megalithic Sites in Britain, was startling: across hundreds of sites, separated by hundreds of miles and built over centuries, the dimensions of stone circles and rows kept coming back to multiples of a single consistent unit of length, which he called the megalithic yard — about 2.72 feet, or 0.829 metres.

This wasn't just circle diameters. Thom found that megalithic builders seemed to prefer using whole-number multiples of the megalithic yard for radii and for the distances between the geometric foci used to construct non-circular rings, and — more demanding still — that they often also wanted the perimeter of a ring to come out to a whole number of megalithic yards, which is mathematically awkward for a true circle given that pi is irrational. To satisfy this, Thom argued, the builders frequently didn't build plain circles at all, but flattened circles, ellipses, and compound "egg" shapes built from arcs of different radii — shapes whose perimeters could be tuned to hit a round number of units in a way a simple circle's could not. He went on to classify these rings into a formal typology: Type A, Type B, and "Type B modified" flattened circles, Type I and Type II eggs, true ellipses, and true circles.

He also proposed that the unit could be subdivided — pointing, controversially, to the fine concentric "cup and ring" carvings found on stones at many megalithic sites as possible evidence of sub-unit marking, though the meaning of these carvings remains genuinely unknown.

Stone circles as astronomical instruments

Thom's second major claim ran alongside the megalithic yard and, if anything, proved even more influential: he argued that the sightlines defined by many circles, rows, and outlying stones pointed toward astronomically significant risings and settings of the Sun, and especially of the Moon at its extreme "standstill" positions — the points, recurring on an 18.6-year cycle (the same lunar nodal cycle at the heart of the Hawkins/Hoyle Stonehenge eclipse debate), where the Moon's rising and setting positions on the horizon reach their northernmost and southernmost extremes.

Thom proposed that Neolithic and Bronze Age astronomer-priests had used these alignments to maintain a working solar calendar, possibly built around eight seasonal markers rather than the four familiar solstice/equinox points — anticipating, in effect, something close to the eight-fold division still faintly preserved in the old Scottish Quarter Days. In doing so, Thom's work — quite independently of Hawkins and Hoyle's Stonehenge-specific claims — helped found the discipline now known as archaeoastronomy: the systematic study of how ancient peoples observed, measured, and built monuments oriented to the sky.

Controversy and reception

Thom's claims met with the same split reaction that greeted Hawkins's Stonehenge Decoded: broad public fascination alongside sustained archaeological resistance. The BBC's flagship Chronicle series ran a full documentary on his work in 1970, and by his own account a leading statistician of the era validated the megalithic yard's statistical case before the Royal Society and British Academy. But many archaeologists remained unconvinced, particularly by the megalithic yard. Aubrey Burl, a leading stone circle specialist, dismissed it outright as a statistical illusion. The core objection was less about Thom's fieldwork — which even critics generally credit as careful and precise — and more about how to interpret a common-sounding measurement recurring across hundreds of sites built by dispersed, non-literate communities over centuries: is that a shared unit of measure carried by cultural transmission, or a statistical mirage produced by human builders naturally favoring round numbers of paces regardless of any single "true" underlying unit?

That debate has never been fully settled. What has shifted substantially in Thom's favor over time is the once-controversial half of his claim: that Neolithic and Bronze Age Britain possessed real observational astronomy, encoded deliberately into monument alignments. That position, radical when Thom first advanced it, is now rarely disputed in serious archaeological circles — even scholars who reject the megalithic yard tend to accept that the orientations themselves were often intentional.

Why he belongs alongside Hawkins and Hoyle

Thom's work sits naturally beside Hawkins's Stonehenge Decoded and Hoyle's On Stonehenge — the same 18.6-year lunar cycle, the same insistence that Neolithic and Bronze Age Britons were capable of sustained, precise, quantitative observation of the sky, and the same pattern of public enthusiasm colliding with entrenched academic skepticism. But Thom's evidence base was broader by an order of magnitude: not one monument decoded by computer, but hundreds of sites, independently surveyed over more than four decades by a professional engineer applying the same rigorous methods he'd used to design wind tunnels and refine bouncing bombs. Whatever the final verdict on the megalithic yard itself, Thom's surveys remain one of the most extensive bodies of primary measurement data ever assembled on Britain's prehistoric monuments — and, for anyone drawn to the idea that whole-number ratios recurring across independent sites are a signal rather than noise, his life's work is hard to dismiss lightly.

A monument built in stages

Stonehenge, on Salisbury Plain in Wiltshire, England, was not built all at once. Archaeologists recognize several main phases of construction spanning roughly 3000 to 1600 BCE. The earliest phase (Stonehenge I) established the circular earthwork bank and ditch and the ring of 56 pits known as the Aubrey Holes, named after the 17th-century antiquarian John Aubrey who first noted them. Later phases brought the smaller bluestones (hauled, remarkably, all the way from the Preseli Hills in Wales) and finally the massive 30–50 ton sarsen stones — including the iconic trilithons and the outer sarsen circle — put in place by what Gerald Hawkins would later call the "Wessex lords," completing the monument in roughly its familiar form around 1650 BCE.

For centuries Stonehenge was treated mainly as an archaeological and antiquarian puzzle — a temple, a burial ground, a gathering place. It took an astronomer, armed with an early computer, to reframe it as something else entirely: a machine for tracking cycles in the sky.

Hawkins and Stonehenge Decoded

Gerald S. Hawkins (1928–2003) was a British-born radio astronomer who became professor and chairman of the astronomy department at Boston University. In two papers published in Nature in 1963 and 1964, he proposed that many of the alignments between stones, archways, and outlying markers at Stonehenge pointed toward significant risings and settings of the Sun and Moon — solstices, equinoxes, and the extreme swings of the Moon's roughly 18.6-year cycle. He went further, arguing that the ring of 56 Aubrey Holes could function as a kind of Neolithic eclipse predictor.

Hawkins fed the site's stone and hole positions into an early IBM 7090 computer — a striking image at the time, an ancient monument decoded by cutting-edge 1960s technology — to model the movements of the Sun and Moon against the monument's geometry and check the statistical significance of the alignments he had found. He published the full case in his popular 1965 book Stonehenge Decoded (written with John B. White).

The core idea behind the Aubrey-Hole eclipse predictor was numerical. The Moon's nodes — the two points where its orbital path crosses the Sun's apparent path (the ecliptic) — regress around the sky once every 18.61 years, and it's this nodal cycle that governs when and where eclipses can occur (the basis of the ancient Saros eclipse cycle). Hawkins noted that 56, the number of Aubrey Holes, is close to three times 18.61 years (19 + 19 + 18 ≈ 56). His proposed method was to move a set of marker stones — he suggested three pairs of black and white stones — around the circle of 56 holes, one hole per year. Certain configurations of the markers, recurring on a predictable schedule, would flag "danger periods" when an eclipse was possible. He claimed this scheme could have let the builders anticipate eclipses to within a few days, and — for the later, more elaborate sarsen-stone phase — he suggested even tighter, hour-level precision was achievable using the sightlines through the trilithon archways.

The book was a sensation. It recast the people who built Stonehenge — popularly dismissed by some archaeologists of the time as unsophisticated — as capable of serious observational astronomy and abstract, cyclical reasoning about the sky. It also provoked a sharp backlash: Richard Atkinson, the leading Stonehenge archaeologist of the day, published a stinging rebuttal in 1966 titled "Moonshine on Stonehenge," dismissing much of Hawkins's statistical case (Atkinson had himself referred to the monument's builders as "howling barbarians," a remark he later regretted).

Hoyle's refinement: On Stonehenge

Fred Hoyle (1915–2001), the eminent Cambridge astrophysicist and cosmologist best known for his work on stellar nucleosynthesis and his advocacy of the Steady State theory of the universe, took Hawkins's eclipse-predictor idea seriously enough to rework it from scratch. In his 1977 book On Stonehenge, Hoyle applied his own astronomical and mathematical rigor to the Aubrey Hole scheme, and concluded that Hawkins's original marker-moving procedure was not quite workable as described — it drifted out of sync with the real sky after a few cycles.

Hoyle proposed an alternative, self-correcting procedure using markers for the Sun, the Moon, and the Moon's nodes moving around the 56 holes at different, carefully chosen rates, with periodic adjustments (moving a marker in the "wrong" direction at certain points) to keep the whole system tracking the true 18.61-year nodal cycle accurately over long stretches of time. In effect, Hoyle treated the Aubrey circle as an analog computer — a physical embodiment of the same kind of cyclical, ratio-based reasoning that shows up throughout the cycles research tradition, where slow astronomical periods are tracked by counting through a fixed number of discrete steps.

Hoyle's scheme was mathematically more elegant and self-correcting than Hawkins's, but it came with its own problem: later critics pointed out that the specific sequence of moves Hoyle's method required was arguably too abstract and specialized for Neolithic astronomers to have plausibly devised without already knowing the answer they were trying to compute — the reconstruction was too clever, in other words, given what could be observed and reasoned about with the naked eye over a human lifetime. So where Hawkins was accused of finding statistically shaky alignments, Hoyle was in effect accused of solving Stonehenge's problem too well.

Where the debate has landed

Neither the Hawkins nor the Hoyle version of the Aubrey Hole eclipse predictor is now accepted uncritically by mainstream archaeology, but the broader legacy of their work has stuck: Stonehenge is today widely treated as having a genuine, deliberate relationship to solar and lunar cycles, at minimum through its well-established solstitial alignment (the famous sunrise/sunset axis), even where the more elaborate eclipse-computer claims remain contested. Hawkins effectively founded the modern field of archaeoastronomy — the study of how ancient peoples observed and encoded the sky in their monuments — and Hoyle's contribution pushed the mathematics of that question as far as it could rigorously go.

Why it belongs alongside cycles research

Stonehenge sits at a striking intersection for anyone interested in cycles: a physical structure, built over centuries by people with no writing system as we'd recognize it, apparently organized around the same nested astronomical periods — the year, the 18.6-year lunar nodal cycle, the Saros eclipse cycle — that recur throughout later cycles literature in completely different guises. Whether or not the Aubrey Holes were literally used as Hawkins or Hoyle proposed, the fact that both a professional astronomer and one of the 20th century's leading astrophysicists judged the underlying cyclical arithmetic to be plausible enough to work out in detail says something about how deeply period-counting and cyclical reasoning run through the human relationship with the sky — right back to the Neolithic.

First published: 2026

Brief summary

Critical overview of the Strauss-Howe generational 'Fourth Turning' theory, noting that no peer-reviewed time-series analysis has been able to statistically distinguish the claimed 80-year periodicity from ordinary stochastic fluctuation.

Article

Theory of Generations (Strauss-Howe 80-Year Cycle: Critical Review) is an encyclopedic/critical overview published by Grokipedia in 2026. It focuses on critical overview of the Strauss-Howe generational 'Fourth Turning' theory, noting that no peer-reviewed time-series analysis has been able to statistically distinguish the claimed 80-year periodicity from ordinary stochastic fluctuation.

Claimed period: ~80 years (four ~20-year generational turnings). It also considers explicitly notes absence of peer-reviewed statistical validation for this periodicity. This gives the cycle claim a specific numerical and evidential setting rather than presenting periodicity only as a visual impression.

The article reports the following result: No peer-reviewed analyses have employed time-series modelling or hypothesis testing to distinguish the proposed 80-year periodicity from stochastic fluctuations or competing economic-demographic drivers. The interpretation is strongest when it survives detrending, autocorrelation controls, structural-break tests and comparison with stochastic or random-walk alternatives.

For cycles researchers, the article brings together strauss-howe theory, generational cycles, fourth turning, 80-year cycle. It is relevant to social-cycle research because apparent waves in historical or behavioural data must be separated from seasonality, autocorrelation, structural change and random walks.

Because this is an encyclopedic/critical overview, it is best used as an accessible introduction or perspective rather than as conclusive evidence. Forum discussion should follow its references back to the primary data and original research wherever possible.

Source details and credits

• Source / publisher: Grokipedia
• Source type: Encyclopedic/critical overview
• URL type: WWW
• Credits: Grokipedia
• URL: https://grokipedia.com/page/Theory_of_generations

First published: 2024

Brief summary

Rigorous statistical testing (Tsay nonlinearity tests) of long-period cycle claims in US homicide rate trends finds the apparent multi-decade 'wave' is likely a statistical artifact of a random walk process rather than a genuine cycle.

Article

Empirical Properties of Crime Rate Trends is a peer-reviewed journal article published by Journal of Contemporary Criminal Justice (Sage) in 2024. It focuses on rigorous statistical testing (Tsay nonlinearity tests) of long-period cycle claims in US homicide rate trends finds the apparent multi-decade 'wave' is likely a statistical artifact of a random walk process rather than a genuine cycle.

The study tests claimed long-period homicide cycles. The study finds apparent wave disappears after differencing, suggesting it is a random-walk artifact rather than genuine periodicity. The data source is panel of 47 large US cities, 1960-2021. This gives the cycle claim a specific numerical and evidential setting rather than presenting periodicity only as a visual impression.

The article reports the following result: Some observers suggest that homicide rates follow long-period cycles. The apparent homicide wave disappears after differencing, strongly suggesting that it is an artifact of the generating process rather than genuine nonlinear cyclicality. The interpretation is strongest when it survives detrending, autocorrelation controls, structural-break tests and comparison with stochastic or random-walk alternatives.

For cycles researchers, the article brings together crime rate trends, homicide cycles, random walk, time-series testing. It is relevant to social-cycle research because apparent waves in historical or behavioural data must be separated from seasonality, autocorrelation, structural change and random walks.

Because it is a peer-reviewed journal article, the article is a strong starting point for discussion in the Sociology forum, although its conclusions should still be compared with later replications and updated datasets.

Source details and credits

• Source / publisher: Journal of Contemporary Criminal Justice (Sage)
• Source type: Peer-reviewed journal article
• URL type: WWW
• Credits: Journal of Contemporary Criminal Justice (Sage)
• URL: https://journals.sagepub.com/doi/full/10.1177/10439862231189979

First published: 2024

Brief summary

Applies a physics-style periodic-signal approach to social data, finding US homicide rates correlate strongly (r=0.87) with a 54-year sine wave, peaking during declining phases of the long Kondratieff economic cycle.

Article

A Hard-Science Approach to Kondratieff's Economic Cycle (Homicides section) is a preprint published by arXiv in 2024. It applies a physics-style periodic-signal approach to social data, finding US homicide rates correlate strongly (r=0.87) with a 54-year sine wave, peaking during declining phases of the long Kondratieff economic cycle.

The analysis focuses on 54 years (homicide rate cycle), correlation r=0.87 with fitted sine wave. The data source is US Census Bureau Statistical Abstract and FBI Crime in the United States, 5-year sampling through 2014. This gives the cycle claim a specific numerical and evidential setting rather than presenting periodicity only as a visual impression.

The article reports the following result: Homicides in the U.S. rise and fall periodically with no particular trend; the correlation with a regular sine wave of 54-year period is r = 0.87, with homicides peaking during the declining phases of the Kondratieff cycle. The interpretation is strongest when it survives detrending, autocorrelation controls, structural-break tests and comparison with stochastic or random-walk alternatives.

For cycles researchers, the article brings together homicide cycles, kondratieff cycle, 54-year sine wave, social periodicity. It is relevant to social-cycle research because apparent waves in historical or behavioural data must be separated from seasonality, autocorrelation, structural change and random walks.

Because it is a preprint, the work should be read alongside later peer-reviewed publications and independent replications. It remains useful because the proposed cycle, dataset and analytical approach are stated clearly enough to be scrutinised.

Source details and credits

• Source / publisher: arXiv
• Source type: Preprint
• URL type: PDF
• Credits: arXiv
• URL: https://arxiv.org/pdf/2410.05285

First published: 2023

Brief summary

Proposes an oscillator-circuit-inspired mathematical model for sociological cycles, illustrated with a ~10-year oscillation found in the historical popularity (citation frequency) of painter Marc Chagall in the UK and Germany.

Article

Sociological Cycles: The Accumulated Discrepancy Between Appearance and Reality as Driver is a preprint published by arXiv in 2023. It focuses on proposes an oscillator-circuit-inspired mathematical model for sociological cycles, illustrated with a ~10-year oscillation found in the historical popularity (citation frequency) of painter Marc Chagall in the UK and Germany.

The analysis focuses on slightly less than 10 years (fashion/popularity cycle). The data source is Google Books culturomics citation-frequency data for Marc Chagall, 20th century. This gives the cycle claim a specific numerical and evidential setting rather than presenting periodicity only as a visual impression.

The article reports the following result: Apart from a slight overall increase, curves of Chagall citation frequency in the UK and Germany both show oscillations with a period slightly less than 10 years, understood as a typical fashion cycle. The interpretation is strongest when it survives detrending, autocorrelation controls, structural-break tests and comparison with stochastic or random-walk alternatives.

For cycles researchers, the article brings together sociological cycles, fashion cycles, chagall popularity, oscillator model. It is relevant to social-cycle research because apparent waves in historical or behavioural data must be separated from seasonality, autocorrelation, structural change and random walks.

Because it is a preprint, the work should be read alongside later peer-reviewed publications and independent replications. It remains useful because the proposed cycle, dataset and analytical approach are stated clearly enough to be scrutinised.

Source details and credits

• Source / publisher: arXiv
• Source type: Preprint
• URL type: PDF
• Credits: arXiv
• URL: https://arxiv.org/pdf/2309.14772

First published: 2013

Brief summary

Applies a nonlinear time-series method to 1975-1993 monthly US robbery and homicide data alongside unemployment figures, searching for dynamical regime shifts and relationships between crime and economic cycles.

Article

Fluctuation of Similarity to Detect Transitions Between Dynamical Regimes: Application to Crime Time Series is a preprint published by arXiv in 2013. It applies a nonlinear time-series method to 1975-1993 monthly US robbery and homicide data alongside unemployment figures, searching for dynamical regime shifts and relationships between crime and economic cycles.

Monthly-resolution analysis of robbery and homicide 1975-1993. The data source is ICPSR Uniform Crime Reports and US Bureau of Labor Statistics unemployment data. The study includes time series graphs. This gives the cycle claim a specific numerical and evidential setting rather than presenting periodicity only as a visual impression.

The authors analyse time series of robberies and homicides in the United States from 1975 to 1993 with monthly resolution, attempting to understand the relationship between unemployment and crime rates over this period. The interpretation is strongest when it survives detrending, autocorrelation controls, structural-break tests and comparison with stochastic or random-walk alternatives.

For cycles researchers, the article brings together crime time series, dynamical regime shifts, homicide and robbery, unemployment. It is relevant to social-cycle research because apparent waves in historical or behavioural data must be separated from seasonality, autocorrelation, structural change and random walks.

Because it is a preprint, the work should be read alongside later peer-reviewed publications and independent replications. It remains useful because the proposed cycle, dataset and analytical approach are stated clearly enough to be scrutinised.

Source details and credits

• Source / publisher: arXiv
• Source type: Preprint
• URL type: PDF
• Credits: arXiv
• URL: https://arxiv.org/pdf/1310.7506

First published: 2013

Brief summary

Applies structural-demographic theory to US and Chinese historical instability data, modeling the superposition of ~50-year cycles on longer secular waves of sociopolitical instability driven by elite overproduction and population pressure.

Article

A Structural-Demographic Analysis of American History is a preprint/working paper published by Peter Turchin (working paper/book manuscript) in 2013. It applies structural-demographic theory to US and Chinese historical instability data, modelling the superposition of ~50-year cycles on longer secular waves of sociopolitical instability driven by elite overproduction and population pressure.

The analysis focuses on ~50-year cycles superimposed on secular waves. The study includes a figure of Chinese political stability index data plotted per 25-year interval from historical records. This gives the cycle claim a specific numerical and evidential setting rather than presenting periodicity only as a visual impression.

The article reports the following result: Long-term dynamics of sociopolitical instability are characterised by a complex mixture of two periodicities: 50-year cycles superimposed on secular waves, a pattern examined here for both the United States and historical China. The interpretation is strongest when it survives detrending, autocorrelation controls, structural-break tests and comparison with stochastic or random-walk alternatives.

For cycles researchers, the article brings together structural-demographic theory, political instability, 50-year cycles, secular waves. It is relevant to social-cycle research because apparent waves in historical or behavioural data must be separated from seasonality, autocorrelation, structural change and random walks.

Because it is a preprint/working paper, the work should be read alongside later peer-reviewed publications and independent replications. It remains useful because the proposed cycle, dataset and analytical approach are stated clearly enough to be scrutinised.

Source details and credits

• Source / publisher: Peter Turchin (working paper/book manuscript)
• Source type: Preprint/working paper
• URL type: PDF
• Credits: Peter Turchin (working paper/book manuscript)
• URL: https://peterturchin.com/wp-content/uploads/2013/09/SDAAS_Sep17.pdf