Hodgetts, Richard M.
The Business enterprise : social challenge, social response
Saunders, 1977
 Buku Teks
Mahathir bin Mohamad, 1925-
The challenge
Pelanduk Publications, 1986
 Buku Teks
Kouzes, James M.
The leadership challenge
Jossey-Bass, 2002
 Buku Teks
Myrdal, Gunnar, 1898-
Challenge to affluence
Pantheon Books, 1963
 Buku Teks
Miner, John B.
The challenge of managing
W.B. Saunders, 1975
 Buku Teks