Ward, Robert
Philippines Summer Institute of Linguistic Translator Philippines Publishers 1968
Buku Teks
McKaughan, Howard P., author
Institute of National Language, 1958
Buku Teks
London: Tiger Books International, 1994,
Buku Referensi
Lucy, Niall, author
Wiley Balckwell, 2016
Buku Teks
Guandola, M.H.
Merriam & Webster, INC, 1989
Buku Teks