1. Michaels, A. S. in “Progress in Separation and Purification,” vol. 2, Wiley, New York (1968) p. 297.
2. Degussa, AG, personal communication.
3. Bueckmann, A. F. GermanPatent 28 41 414 (1979).
4. US Patent 410 8875 (1978).
5. Kula, M. R., et al., this volume.