Buss, Claude Albert, author
Mamillan, 1955
Buku Teks
Gunther, John, 1901-1970, author
Harper & Brothers, 1942
Buku Teks
Stamp, L. Dudley (Laurence Dudley), 1898-1966, author
Methuen, 1950, 1952, 1967
Buku Teks
Weale, B.L. Putnam
MacMillan , 1908
Buku Teks
edited by Ng Chee Yuen, Charla Griffy-Brown
International Development Research Institute, 2000
Buku Referensi