context: Earlier papers studying problems solvable by Turing machines with specific bounded resources include  John Myhill's definition of linear bounded automata (Myhill 1960), Raymond Smullyan's study of rudimentary sets (1961), as well as Hisao Yamada's paper on real-time computations (1962). Somewhat earlier, Boris Trakhtenbrot (1956), a pioneer in the field from the USSR, studied another specific complexity measure. As he remembers:
question: రేమండ్ సల్లివన్ ఏ సంవత్సరంలో ప్రాథమిక సెట్ల అధ్యయనాన్ని ప్రచురించాడు?
answers: 1961 1961 1961