Steyaert, Thomas A.
McGraw-Hill, 1975
Buku Teks SO
Artikel Jurnal
White, Robert W.
Holt, Rinehart and Winston, 1976
Buku Teks SO
edited by John Keep with the assistance of Liliana Brisby
Frederick A. Praeger, 1964
Buku Teks SO
Oberdorfer, Don
Basic Books, 2001
Buku Teks