Song Jian's own words, quoted by Greenhalgh from his 1986 essay, date his first exposure to population-systems-analysis to a 1978 European visit — a second independent witness converging against Olsder's 1975 account

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Susan Greenhalgh's 2003 Population and Development Review article states, in its own narrative voice, that "the group's leader, Song Jian, got the idea for this project on a delegation visit to Europe in 1978" (p. 170), then quotes Song directly, citing his own 1986 conference paper: "After more than ten years' isolation from the outside world, during a visit to Europe in 1978, I happened to learn about the application of systems analysis theory by European scientists to the study of population problems with a great success. ... I was extremely excited about these documents and determined to try the method of demography" (Song 1986: 2-3, quoted p. 170).

This is Song's own first-person account of when he first encountered this material, not a secondary gloss. It converges with, and independently strengthens, Liang Zhongtang's independent 2009 dating of the same event to 1978 — a second independent witness (Liang's essay, and now Song's own quoted words) placing Song's "learning" of population-systems-analysis methods in 1978. Greenhalgh's narrative sentence is not a third witness: it is her own paraphrase of this same passage, which she quotes two sentences later as its only support, and the mid-1978 Helsinki dating in her 2005 China Quarterly article is footnoted (fn 17, p. 258) to the same Song essay. Every dating Greenhalgh supplies on this question therefore runs back through Song's own retrospective. The two witnesses stand against Geert Jan Olsder's single, uncorroborated, 49-years-later account of a 1975 Twente origin (claim-olsder-1975-account-contradicts-liang-2009-pre-1978-dating). It does not by itself disprove the 1975 Twente conversation happened — Olsder could have described his group's population research to Song in 1975 without it registering as the "systems analysis theory" epiphany Song later dates to 1978 — but it is the first primary-adjacent quotation in Song's own voice the vault has read on this question, and it sharpens the existing citation-trail observation from "does not resolve" toward "cuts against": two independent witnesses now date the "first exposure" moment to 1978, neither mentions a 1975 visit, and the documentary trail that touches dating rests on 1976-78 material compatible with, but not proof of, a post-1975 acquisition. Two witnesses is a weaker ledger than three, and one of the two is the interested party — but it is still one more than the single account on the 1975 side.