Cohen, Nathan Edward, author
National Ass. of Workker, 1964
Buku Teks
Davis, Keith, 1918-, author
McGraw-Hill, 1989
Buku Teks
compiled and edited by M.G. Rao
Discovery Publishing House, 1993
Buku Teks
Davis, Keith, 1918-, author
McGraw-Hill, 1989
Buku Teks
Mukherjee, Nilanjana, author
Bank Dunia, 2006
Buku Teks