Varma, S.P., author
Radja Grafindo Persada, 2003
Buku Teks
Sargent, Lyman Tower, author
Wadsorth Thompson Learning, 2003
Buku Teks
Routledge, 1993
Buku Teks
Baradat, Leon P., author
Prentice-Hall, 1991
Buku Teks
Canning, Joseph
Routledge, 1996
Buku Teks