1. Bertram, S. H., Rec. Trav. Chim. Pays Bas 46:397 (1927).
2. Jantzen, E., and H. Andreas, Ber. 92:1427 (1959).
3. Jantzen, E., and H. Andreas, Ibid. 94:628 (1961).
4. Richau, W., Ph. D. Dissertation, University of Hamburg (1953).
5. White, H. B., and F. W. Quackenbush, JAOCS 39:511 (1962).