Pilcher, Rosamunde
Coronet Books, 1990
Buku Teks
Nation, I.S.P., author
Cambridge University Press, 2013
Buku Teks
Waters, S. J., author
NCC Publications, 1979
Buku Teks
London, Keith R., author
Petrocelli Books, 1974
Buku Teks
Clason, W. E., 1898-, author
Elsevier Scientific Publishing, 1976
Buku Referensi