The cosine-0.85 bipartite pairing between the Greenhalgh/Kwakernaak/Song-1981 claim and the Kaelbling/Åström-1998 claim is a confirmed common-ancestor bridge through A.A. Fel'dbaum, asymmetric in kind and date

feldbaumsong-jiankwakernaakastromkaelblingpomdpcontrol-theorycyberneticscitation-genealogyperson-bridgeembedding-bridge-checkcross-domain-bridgecross-time-bridge

A retrieval-index pairing linked claim-greenhalgh-2003-article-documents-kwakernaak-1977-citation-in-song-1981 (Dutch population-cybernetics reaching a Chinese policy group) and claim-kaelbling-1998-cites-astrom-1965-as-pomdp-origin (Swedish control theory reaching a canonical AI-planning paper) as unlinked neighbors at cosine 0.85, sharing no vocabulary by construction. Chasing both legs to their primaries confirms the resemblance is a real connection, not a false friend — but an indirect one, resting one hop back on a single shared figure: A.A. Fel'dbaum.

On the Greenhalgh/Kwakernaak/Song side, Fel'dbaum personally taught Song Jian control theory during Song's early-1950s Moscow posting (claim-song-jian-studied-under-feldbaum-in-moscow) — years before Song's group's 1981 published argument cited Kwakernaak's 1977 population-policy paper. On the Kaelbling/Åström side, Åström's own 1965 paper cites Fel'dbaum by name in its closing Notes section, alongside Bellman, Pontryagin, and Kolmogorov (claim-astrom-1965-notes-section-cites-feldbaum-pontryagin-kolmogorov-lineage).

The two channels reaching Fel'dbaum are not the same shape. The Song side is personal and oral — face-to-face instruction datable to 1953, roughly seven years before Fel'dbaum's own dual-control formalism (claim-feldbaum-1960s-dual-control-formalized-exploration-exploitation-tradeoff) existed, so the teaching cannot itself have transmitted the specific ideas that later appear in Kwakernaak's paper — Song's later exposure to Western systems-cybernetics work is the more likely route for that. The Åström side is textual and contemporaneous — a 1965 paper citing a specific 1962 paper in its own bibliography. Neither Kwakernaak and Åström, nor Song Jian and Kaelbling/Littman/Cassandra, show any direct connection in any source read this session or elsewhere in the vault; the bridge is a shared ancestor, not a horizontal link between the two pairs the embedding flagged.

This sharpens, rather than duplicates, observation-feldbaum-person-bridge-invisible-to-vault-bridge-tool, which established Fel'dbaum as a person-bridge between the vault's Song Jian cluster and its Kalman/optimal-control cluster in general. This note pins the bridge to the exact two claims the vault's own retrieval flagged as suspiciously similar, and adds that the two paths differ in kind and in date.