1. Admiral Ruge Archives, Brewer Sc. Library, Richland Center, Wisconsin
2. Astronomy, January 2001
3. P.C. Davies, J. Brown, Superstring: A Theory of Everything? 1988
4. Guinness Book of Records, 2001
5. E.E. Escultura, The mathematics of singularities, in: Transactions of National Academy of Science and Technology, XIV, Manila, pp. 141–153