1. Cogswell, F. N., Appl. Polym. Symp.27, 1 (1975).
2. White, J. L., Appl. Polym. Symp.33, 31 (1978).
3. Petrie, C. J. S., Elongational Flow, Pitman (London 1979).
4. M�nstedt, H., Joint Meeting of British, Netherlands and Italian Societies of Rheology (Pisa 1977).
5. Laun, H. M., H. M�nstedt, Rheol. Acta17, 415 (1978).