Thanks. Got it. That's a lot of stuff and a lot of trails. No doubt it was a KGB operation (at least they supervised it or received occasional progress reports), back in Moscow in June 1971.
Another trail would be Hanoi's links to the antiwar press. The Soviets and North Vietnamese had several front news outlets networked in the US with the Institute for Policy Studies (IPS) and such groups--Liberation News Service (LNS, linked to Raymond Mungo and Marshall Bloom), Dispatch News Service (linked to KGB agent Wilfred Burchett, Philip Stern and Richard Barnet of IPS, Seymour Hersh, and Gary Porter, who later shows up as Kerry's legislative aide in the 1980s). I found a 1972 book by Hersh which mentions in the footnotes, "For information on the allegations regarding prisoner abuses, contact the Vietnam Veterans Agains the War. . .The testimony of its 'Winter Soldier' hearings, held in January 1971, received scant newspaper attention at the time, although much of the proceeedings were published in the 'Congressional Record' on April 6 and 7, 1971. A series of similar hearings has been sponsored by the Citizens Commission of Inquiry (CCI). . .which was organized in November, 1969, following the first public disclosures of the My Lai 4 massacre. . ." It appears that Hersh's own work on My Lai--which was initially publicized by Dispatch News Service--helped spark the CCI/VVAW "war crimes" investigation (Nicosia actually says as much on 73-74 of his book where he credits Hersh's work with inspiring Winter Soldier). It stands to reason that whichever agents of Moscow and Hanoi were involved with Hersh and Dispatch News would've also taken an interest in Winter Soldier.
Jane Fonda would've been one of their probable contacts, as her and Tom Hayden supported Winter Soldier before there was a split between VVAW/Fonda and CCI over her support of Mark Lane (who didn't get along with the CCI's Robert Jay Lifton, if I recall right; and Lifton was linked to the IPS' Richard Falk--who testified at the CCI's "hearings"--and Cora Weiss; was this dispute a "party discipline" issue?). Nicosia, 77, mentions that in conjunction with Fonda, the CCI's Tod Ensign and Jeremry Rifkin were aided by the CP's Phil Spiro, and Nicosia, 82 says Ensign sent a representative to the Swedish CP, which was conducting a similar inquiry.
Hersh also mentions some more names of note:
"On April 26-29, 1971, a number of former GIs and officers testified about war crimes before an ad hoc Congressional committee chaired by Representative Ronald V. Dellum[s], California Democrat. . .An excellent compilation of alleged American violations of international law in South Vietnam. . .is 'In the Name of America', a study published in January, 1968, by the Clergy and Laity Concerned about Vietnam [CALCAV]. . .Also see 'Crimes of War', edited by Richard A. Falk and Robert Jay Lifton. . ." Of the above names, Dellums, Falk, and Lifton were involved in Winter Soldier, while CALCAV had been sending delegations to Hanoi in the 1960s (they were cofounded by Daniel Berrigan, who went to Hanoi in 1968 and published his diary of the trip as the book "Night Flight to Hanoi").