found: Whitemore, H. Pack of lies, 1983:p. 9 (Helen Kroger; Soviet spy; 1969 exchanged for a Briton jailed in Moscow)
found: Pisʹma iz ti︠u︡rem Ee Velichestva, 2001:v. 1, t.p. (Khelen Kroger) p. ix (Koėn Leontina Vladislavovna) p. 4 of cover ("Khelen Kroger" was the pseudonym of Leontina Tereza Koėn)
found: Berliner Zeitung WWW home page, Dec. 20, 2002:(Leontina Cohen)
found: Spy book, c1997:(Lona Cohen; 1913-1992; used cover name Helen Kroger)
found: Spies, c1997:(name before marriage Leona or Lona Petka; from Adams, Mass.)