O`Shaughnessy, John, author
George Allen and Unwin, 1974
Buku Teks
McNulty, James E., author
University of Pennsylvania Press, 1964
Buku Teks
Allen, Louis A., author
McGraw-Hill Kogakusha, 1958
Buku Teks
Brech, E.F.L., author
Longmans, Green & Co. , 1957
Buku Teks
Brech, E.F.L., author
Longman , 1970
Buku Teks