Wells, S.J.
Cambridge University Press , 1964
Buku Teks
Stannard, Harold, author
Adam and Charles Black, 1949
Buku Teks
McCue, Janice Helen, author
The Scarecrow Press , 1988
Buku Teks
Nia Setianingtias, author
Fakultas Ekonomi dan Bisnis Universitas Indonesia, 2008
UI - Tesis (Open)
Alford, B.W.E., author
Macmillan, 1988
Buku Teks