Erricker, B.C.
Hodder & Stoughton , 1981
Buku Teks
Sellers, Gene R.
WB. Saunders, 1977
Buku Teks
Runyon, Richard P., author
Ill. Richard D. Irwin , 1982
Buku Teks
Walpole, Ronald E., author
Macmillan, 1968
Buku Teks
Freund, John E., author
Prentice-Hall, 1980
Buku Teks