Asa gray : american botanist, friend of Darwin /

por Dupree, A. Hunter
Publicado 1988

Darwiniana : essays and reviews pertaining to Darwinism. /

por Gray, Asa 1810-1888
Publicado 1963

The plan of ST. Gall : a study of the architecture and economy of, and life in a paradigmatic carolingian monastery /

por Horn, Walther Wilhelm Adolf 1908-1995
Publicado 1979