1. L. Steen, J. Seebach, Counterexamples in Topology (Holt, Rinehart and Winston, 1970)
2. C. Brans, On Unified Field Theories. Undergraduate thesis, Loyola University (1957) (Unpublished)
3. P. Dirac, Proc. Roy. Soc. (London) Al65, 199 (1938)
4. J. Barbour, H. Pfister (ed.), Mach’s Principle v. 6 of Einstein Studies (Birkauser, 1995)
5. D. Sciama, Month. Not. Royal Astron. Soc. 113, 34 (1953)