Hickler, Holly
Allyn and Bacon, Inc., 1980
Buku Teks SO
Sharples, Mike, 1952-
Ellis Horwood Limited, 1985
Buku Teks SO
Johnson, Falk S.
Houghton Mifflin, 1965
Buku Teks
Guthrie, L.O.
Macmillan, 1956
Buku Teks SO
Southwell, E.A.
Longmans, Green, 1947
Buku Teks SO