Connor, L.R.
Sir Isaac Pitman & Sons, 19--
Buku Teks
Johnson, Palmer O., author
Prentice-Hall, 1953
Buku Teks
Kendall, M.G., author
Griffin , 1968
Buku Teks
Huntsberger, David V., author
Allyn and Bacon, 1970
Buku Teks
Games, Paul A., author
McGraw-Hill, 1967
Buku Teks