Postma, Antoon
Arnoldus Press, 1972
Buku Teks
Lopez, Violeta B.
University of the Philippines Press, 1976
Buku Teks
Dozier, Edward P.
Holt, Rinehart and Winston, 1967
Buku Teks
Kinloch, Graham C., author
Prentice-Hall, 1979
Buku Teks
Kinloch, Graham C., author
Prentice-Hall, 1979
Buku Teks