Buku Teks
T. Buckley [at al.]
International Development Program of Australian Universities and Colleges Limited,, 1985
Buku Teks
Clyde F. Coombs, editor-in-chief
McGraw-Hill, 1972
Buku Referensi
Clyde F. Coombs, Jr., editor in chief
McGraw-Hill, 1995
Buku Referensi
Kunst, Jaap, 1891-1960, author
Martinus Nijhoff , 1968
Buku Teks