editor, Laurence Urdang, Stuart Berg Flexner
Random House, 1968
Buku Referensi
Summers, Della
Pearson Education Limited, 2010
Multimedia
Pearson Education Limited, 2010
Buku Referensi
Rosenthal, Marilyn S., author
Longman Inc., 1987
Buku Referensi
McAlpin, Janet, author
England: Longman Group, 1988,
Buku Referensi