Beck, Carlton E., author
Penn International Textbook, 1969
Buku Teks
Redfield, Robert, author
University of Chicago Press , 1962
Buku Teks
edited by F.C. Bartlett
Kegan Paul, Trench, 1946
Buku Teks
Hunt, Elgin F., author
MacMillan, 1987
Buku Teks
Hunt, Elgin F., author
Macmillan, 1962
Buku Teks