Casanave, Christine Pearson
Prentice-Hall, 1986
Buku Teks
Barnett, E. de Barry, author
Longmans Green, 1957
Buku Teks
Blass, Laurie
Prentice-Hall, 1985
Buku Teks
Berkeley University of California Press 1948
Buku Teks
Hague, Douglas C., author
Longmans, Green, 1955
Buku Teks