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.
Čikaški stil citiranja (17. izdanje)ebrary, Inc, i 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 način citiranja (9. izdanje)ebrary, Inc, i John F. Wippel. The Ultimate Why Question: Why Is There Anything at All Rather than Nothing Whatsoever? Catholic University of America Press, 2011.
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