1. J. W. N. Sullivan, The Limitations of Science. Viking, New York, 1933
2. W. James, A Pluralistic Universe. Macmillan, New York, 1909
3. J. Hick, editor, The Existence of God. Macmillan, New York, 1964
4. A. Guillaume, Islam. Penguin, Harmondsworth, Middlesex, UK, 1954
5. A. Flew, editor, Body, Mind, and Death. Macmillan, New York, 1964