Wang, Jianping
Curzon, 2001
Buku Referensi
March, Benjamin
Waverly Press, 1935
Buku Teks SO
Sass, John E.
Iowa State University Press, 1994
Buku Teks
Soothill, W.E. (William Edward)
Motilal Banarsidass Publishers Private Limites, 1937
Buku Referensi
Thomas, T.A.
McGraw-Hill, 1978
Buku Teks SO