Bowling, Ann
Open University Press, 2006
Buku Teks
Steven S. Coughlin, Selina A. Smith, and Maria E. Fernandez, editors
Oxford University Press, 2017
eBooks
Koch, Tina
Blackwell Publishing, 2006
Buku Teks
Shi, Leiyu
Delmar Cengage Learning, 2008
Buku Teks
Rice, Pranee Liamputtong
Oxford University Press, 1999
Buku Teks