1. FLACHS , G. H. , 1967 , Ph.D. dissertation , Michigan State Univ .
2. FUKAO , T. , 1970 ,Proc. IF AC Kyoto Symp, on Syst. Engng Approach to Comput. Control, p. 376 ; 1971, I.E.C.E. Japan Trans, (in Japanese), 54-c, 1141 .
3. Some Notes on Stability Problems of Probabilistic Automata