Central and Eastern Europe: the challenge of transition
edited by Regina Cowen Karp
Oxford University Press, 1993
 Buku Teks
Black C.E.
Challenge in Eastern Europe; 12 essays; foreword / by Joseph C. Grew
Rutgers Univ. Press, 1954, 1954
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Mahathir bin Mohamad, 1925-
The challenge
Pelanduk Publications, 1986
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Kouzes, James M.
The leadership challenge
Jossey-Bass, 2002
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Myrdal, Gunnar, 1898-
Challenge to affluence
Pantheon Books, 1963
 Buku Teks