Taylor, Overton H.
McGraw-Hill Kogakusha, 1960
Buku Teks SO
Roll, Eric
Prentice-Hall, 1959
Buku Teks SO
Beaud, Michel
Routledge, 1997
Buku Teks SO
Haney, Lewis H.
Macmillan, 1949
Buku Teks SO
edited by David Greenaway, Michael Bleaney, and Ian Stewart
Routledge, 1991
Buku Referensi