Παραπομπή σε μορφή APA (7η εκδ.)

Wippel, J. F. (2011). The ultimate why question: Why is there anything at all rather than nothing whatsoever? Catholic University of America Press.

Παραπομπή σε μορφή Chicago (17η εκδ.)

Wippel, John F. The Ultimate Why Question: Why Is There Anything at All Rather than Nothing Whatsoever? Washington, D.C.: Catholic University of America Press, 2011.

Παραπομπή σε μορφή MLA (8th εκδ.)

Wippel, John F. The Ultimate Why Question: Why Is There Anything at All Rather than Nothing Whatsoever? Catholic University of America Press, 2011.