APA-ийн эшлэл(7 дахь хэвлэлт)

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.

Чикаго-гийн эшлэл (17 дахь хэвлэлт)

ebrary, Inc, ба 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.

MLA -ийн эшлэл (9 дэх хэвлэлт)

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