The attempts of the Council of Europe to adopt a convention on the non-applicability of statutory limitations to crimes against humanity preceded those of the United Nations. When the United Nations took up the question in 1965, the Council of Europe suspended its efforts. The U.N. Convention, however, which was adopted on 26 November 1968 seemed unacceptable to most members of the Council of Europe because of its broad definition of "crimes against humanity". The present Convention uses a narrower definition and, unlike the U.N. Convention, limits its applicability to cases for which the statutory limitation period has not expired at the time of the entry into force of it.
D.Schindler and J.Toman, The Laws of Armed Conflicts, Martinus Nijhoff Publishers, 1988, pp.933-936.