Solomon, R.C., author
London DP Publications 1993,
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Solomon, R.C., author
DP Publications, 1992
Buku Teks
Copeland, Richard W., author
Macmillan, 1970
Buku Teks
Armstrong, James W., author
Macmillan, 1976
Buku Teks
Campbell, Hugh G., author
Macmillan, 1974
Buku Teks