Mahathir bin Mohamad, 1925-
The challenge
Pelanduk Publications, 1986
 Buku Teks SO
Fathia Amalia Putri
Tantangan dan Strategi Sistem Penghantaran Obat Tertarget Kolon = Challenge and Strategy for Colon Targeting Drug Delivery System
Fakultas Farmasi Universitas Indonesia , 2020
 UI - Skripsi Membership
Kouzes, James M.
The leadership challenge
Jossey-Bass, 2002
 Buku Teks SO
Myrdal, Gunnar, 1898-
Challenge to affluence
Pantheon Books, 1963
 Buku Teks
The challenge of management
edited by Alan M. Glassman
A Wiley/Hamilton Publication, 1978
 Buku Teks