Diamond, William
Stevens & Sons, 1947
Buku Teks SO
Prague: Orbis, 1958
Buku Teks
Blackwell Publishers for the United Nations Industrial Development Organization, 1992
Buku Teks
Salem Press , 1992
Buku Referensi
Schatten, Fritz
Frederick A. Praeger, 1966
Buku Teks SO