Παραπομπή σε μορφή APA (7η εκδ.)

ebrary, Inc, & 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.)

ebrary, Inc, και John F. Wippel. 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 (9th εκδ.)

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