Saso, Mary
Abt Books, 1982
Buku Teks SO
Basil Blackwell for the United Nations Industrial Development Organization, 1991
Buku Teks
Blackwell, 1990
Buku Teks SO
Vance, Stanley C.
Prentice-Hall, 1961
Buku Teks
Mund, Vernon A.
Appleton-Century-Crofts, 1971
Buku Teks SO