Tester, Keith
Routledge, 1992
Buku Teks
Symon, Keith R.
Addison-Wesley, 1971
Buku Teks
Keith, Harold
A HarperKeypoint Book, 1957
Buku Teks
Rugh, Roberts, author
Burgess , 1971
Buku Teks
Roberts, Richard A., 1935-, author
Massachusetts Addison-Wesley, 1992
Buku Teks