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
Green, George S.
Holt, Rinehart and Winston, 1972
Buku Teks SO
Guthrie, L.O.
Macmillan, 1956
Buku Teks SO