Zwemer, S. M. (1907). Islam, a challenge to faith: Studies on the Mohammedan religion and the needs and opportunities of the Mohammedan world from the standpoint of Christian missions. Student volunteer movement for foreign missions.
توثيق أسلوب شيكاغو (الطبعة السابعة عشر)Zwemer, Samuel Marinus. Islam, a Challenge to Faith: Studies on the Mohammedan Religion and the Needs and Opportunities of the Mohammedan World from the Standpoint of Christian Missions. New York: Student volunteer movement for foreign missions, 1907.
توثيق جمعية اللغة المعاصرة MLA (الطبعة الثامنة)Zwemer, Samuel Marinus. Islam, a Challenge to Faith: Studies on the Mohammedan Religion and the Needs and Opportunities of the Mohammedan World from the Standpoint of Christian Missions. Student volunteer movement for foreign missions, 1907.