Felix Christian
Klein

Universität Göttingen


Johannes Franz
Hartmann

Kuffner-Sternwarte


Richard
Schorr

University of Hamburg (Astronomy Tree)


Walter
Baade

Mount Wilson Observatory




Bart J.
Bok

University of Arizona




George
Wallerstein

University of Washington


Theodore P.
Snow

CU Boulder

Ralph Y.
Shuping

CU Boulder
(Options)

Ralph ShupingX