Gibney contributed substantial commentary to "The Penkovskiy Papers" (1965). Oleg Penkovskiy was a colonel in the GRU (Soviet military intelligence). The book is based around English translations of classified Russian texts, which had previously been provided to American intelligence by Penkovskiy. It presents an insider's view of Soviet intelligence agencies and their trade craft. Its Russian author and source, after a publicized trial, had been executed by the Soviet government in 1963. This book and another co-written with Deriabin made use of material requested from the CIA.