Proceedings of the National Academy of Sciences of the United States of America. 1/8/2002, Vol. 99 Issue 1, p178. 6p. 4 Color Photographs, 3 Black and White Photographs, 1 Diagram, 2 Graphs.
Proceedings of the National Academy of Sciences of the United States of America. 1/8/2002, Vol. 99 Issue 1, p173. 5p. 1 Color Photograph, 1 Black and White Photograph, 1 Diagram, 1 Graph.