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.
Lua i Stíl Chicago (17ú heag.)ebrary, Inc, agus 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.
Lua MLA (9ú heag.)ebrary, Inc, agus John F. Wippel. The Ultimate Why Question: Why Is There Anything at All Rather than Nothing Whatsoever? Catholic University of America Press, 2011.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.