1. van Es, H., (Shell, Amsterdam) has informed us that he will shortly publish an almost direct method.
2. Berry, J. P. andJ. Batchelor, in: Polymer Systems, Deformation and Flow, Edit.Wetton andWharlow, p. 188 (London 1968).
3. Diesselhorst, H. undH. Freundlich, Physik-Ztg.16, 420 (1915).
4. Freundlich, H., F. Stapelfeldt undH. Zocher, Z. Physik Chem.114, 161, 190 (1925).
5. Snellman, O. undY. Bjornstahl, Koll. Beihefte52, 403 (1941).