1. private communication, Ann Arbor, Michigan, February 22, 1977.
2. private communication, Stamford, Connecticut, January 24, 1977.
3. private communication, Amersfoort, Netherlands, March 16, 1977.
4. private communication, Rochester, New York, February 21, 1977.
5. private communication, Wetzlar, Germany, December 6, 1977.