1. S. Guiasu:Compt. Rend.,216, 1179 (1965);S. Guiasu:Rend. Acad. Lincei,39, 447 (1966).
2. G. Racah:Rend. Acad. Lincei,25, 223 (1937);P. Caldirola:Rend. Ist. Lomb. Scienze,72, 379 (1939).
3. P. Caldirola:Nuovo Cimento,18, 393 (1941).
4. I. E. Farquhar:Ergodic Theory in Statistical Mechanics (London, 1964) (see particularly Sect.4 and Sect.4).
5. seeCaldirola (3). For other contributions to the quantization of nonconservative systems see:E. Kanai:Progr. Theor. Phys.,3, 440 (1948);