Bailey, Joe
Routledge & Kegan Paul, 1980
Buku Teks
Brym, Robert J., author
Wadsworth and Cengage Learning, 2013
Buku Teks
Ross, H. Laurence (Hugh Laurence), author
McGraw-Hill, 1973
Buku Teks
Bell, Earl H.
Harper & Row, 1965
Buku Teks
Rotterdam University Press, 1974
Buku Teks