Proceedings of the National Academy of Sciences of the United States of America. 5/28/2002, Vol. 99 Issue 11, p7548. 6p. 3 Color Photographs, 8 Diagrams.
Proceedings of the National Academy of Sciences of the United States of America. 08/17/99, Vol. 96 Issue 17, p9695. 6p. 4 Color Photographs, 1 Black and White Photograph.