Liang Zhongtang's 2009 essay corroborates, independently of Greenhalgh, that Song Jian's population-forecasting method arrived via a 1978 academic trip to Europe

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In the same 2009 essay where he rejects Song Jian's causal role in the one-child policy (see claim-liang-zhongtang-2009-rejects-song-jian-causal-self-credit), Liang Zhongtang names Song "是個異數" ("an anomaly" within the demography field) and gives the origin of Song's method — "1978年， 在一次赴歐洲的學術訪問中，東道主向宋健等客人提供了不少用控制論和系統工程方法預測 人口的資料" — translation for this note, not independently cross-checked against a published English rendering: "In 1978, during an academic visit to Europe, the host provided Song Jian and other guests with a substantial amount of material using cybernetics [control theory] and systems-engineering methods to forecast population. Before this, Song Jian and his fellow engineers — who worked on rocket launches and orbital trajectory design — had never heard that cybernetics and systems-engineering methods could also be used for population forecasting."

This matters because it comes from the scholar most committed to denying Song's causal role in the policy, yet it does not dispute that Song's method was foreign-derived and arrived via a 1978 trip abroad — corroborating, from the opposite side of the historiographical dispute, the same underlying fact recorded in Greenhalgh's account of Song's 1978 encounter with the Club of Rome's cybernetics. Liang's essay does not name the country, city, host institution, or conference — "赴歐洲" ("visit to Europe") is as specific as the text gets — so it corroborates the year and the general fact of foreign cybernetics/systems-engineering exposure without confirming the 1978 IFAC World Congress in Helsinki as that specific trip. Whether the two are the same event is tracked at question-song-jian-1978-europe-trip-identify-as-ifac-helsinki-congress.