[1] N.J.A. Sloane, The persistence of a number, J. Recreational Math. 6(1973), 97-98 (zip)

[2] Mark R. Diamond, Daniel D. Reidpath, A counterexample to a conjuncture of Sloane and Erdös, J. Recreational Math. 1998 29(2), 89-92 (pdf) (bad copy)

[3] Richard K.Guy, Unsolved Problems in Number Theory, Second Edition, 1994

[4] Sascha Kurz, Persistencen in verschiedenen Basen (german), unpublished (read with caution, cause the author is still learning math ;-) ), 2001 (dvi) (ps) (pdf) (tex)

[5] N.J.A. Sloane (2001), The On-Line Encyclopedia of Integer Sequences, published electronically at http://www.research.att.com/~njas/sequences/.

6. Links

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