Eidelberg, Paul, author
Free Press, 1968
Buku Teks
Browne, Glenn J.
Bowling Green State University, 1986
Buku Teks
edited by Ralph B. Winn
Littlefield, Adams, 1963
Buku Teks
Bartholomew, Paul C., author
W.M.C. Brown, 1951
Buku Teks
Gellhorn, Walter, author
Macmillan, 1961
Buku Teks