1. E. H. Squires:Complex Angular Momentum and Particle Physics (New York, 1963). This book contains the references to the original papers.
2. H. Joos: inLectures in Theoretical Physics, vol.7 A, Edited byW. E. Brittin andA. O. Barut, Boulder, Colo., 1965), p. 132.
3. E. P. Wigner:Ann. Math.,40, 149 (1939).
4. V. Bargmann:Ann. Math.,48, 568 (1947).
5. L. Sertorio andM. Toller:Nuovo Cimento,33, 413 (1964).