Sweedlum, Verne S., author
American Book Company, 1956
Buku Teks
edited by Alan Bryman & Robert G. Burgess
Sage, 1999
Buku Teks
Moody, Joseph N.
N.Y. Doubleday , 1958
Buku Teks
Cohen, Abner, author
Routledge & Kegan Paul, 1974
Buku Teks
Briggs, Lawrence Palmer
The American Philosophical Society, 1951
Buku Teks