The following selected bibliographical summary contains a compilation of the material by the individual countries. Abbreviations used for distinguishing the individual countries concerned: Bulg. = People's Republic of Bulgaria; Czechosl. = Czechoslovak Socialist Republic; Germ. = German Democratic Republic; Hung. = Hungarian People's Republic; Pol. = Polish People's Republic; Rum. = Socialist Republic of Rumania; USSR = Union of Soviet Socialist Republics; Yug. = Socialist Federative Republic of Yugoslavia. In order to facilitate identification, the titles are given in the language of the original publication, with an English or French translation of the title in the required cases.