Feiring, Bruce R.
Sage University Paper, 1986
Buku Teks SO
Thie, Paul R.
John Wiley & Sons, 1979
Buku Teks SO
Chung, An-Min
Charles E. Merill Publishing CO., 1963
Buku Teks SO
Campbell, Hugh G.
Prentice-Hall, 1977
Buku Teks SO
Djati Kerami
Universitas Terbuka, 2008
Buku Teks SO