Kelsen, Hans
Introduction to the problems of legal theory
Clarendon Press Oxford, 1992
Buku Teks
Dixon, John D.
Problems in group theory
Blaisdell, 1967
Buku Teks
Spiegel, Murray R.
Theory and problems of statistics
McGraw-Hill, 1961
Buku Teks
Dixon, John D.
Problems in group theory
Blaisdell, 1967
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Scheid, Francis
Theory and problems of computers and programming
McGraw-Hill, 1983
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