Wales, Katie, author
Longman , 1991
Buku Referensi
compiled by Howard P. McKaughan, Batua A. Macaraya
University of Hawaii Press, 1967
Buku Referensi
Pei, Mario A., author
Peter Owen, 1958
Buku Referensi
Angeles, Peter A., author
Barnes and Nobles, 1981
Buku Referensi
Oxford University Press, 1983
Buku Referensi