Rocamora, J. Eliseo
Philippine Center for Advanced Studies, 1975
Buku Teks
Brown, David
Routledge, 1994
Buku Teks
Brown, David
Routledge, 1996
Buku Teks
Cady, John F.
Harvard University Press, 1976
Buku Teks
Olmstead, Clifton E.
Prentice-Hall, 1960
Buku Teks