@inproceedings(cowles,
 author       = {John Cowles and Ruben Gamboa},
 year         = {2014},
 title        = {Equivalence of the Traditional and Non-Standard Definitions of Concepts from Real Analysis},
 editor       = {Freek Verbeek and Julien Schmaltz},
 booktitle    = {Proceedings of the Twelfth International Workshop of the ACL2 Theorem Prover and its Applications (ACL2-2014)},
 address      = {Vienna, Austria},
 pages        = {89--100},
 doi          = {10.4204/EPTCS.152.8},
)
@book(dunham,
 author       = {William Dunham},
 year         = {1999},
 title        = {Euler: The Master of Us All},
 publisher    = {Mathematical Association of America},
)
@phdthesis(gamboa,
 author       = {Ruben Gamboa},
 year         = {1999},
 title        = {Mechanically Verifying Real-Valued Algorithms in ACL2},
 school       = {University of Texas at Austin},
)
@article(nelson,
 author       = {Edward Nelson},
 year         = {1977},
 title        = {Internal Set Theory: A New Approach to Nonstandard Analysis},
 journal      = {Bulletin of the American Mathematical Society},
 volume       = {83},
 pages        = {1165--1198},
 doi          = {10.1090/S0002-9904-1977-14398-X},
)
@misc(wiki,
 year         = {2015},
 title        = {Perfect Number: From Wikipedia, the free encyclopedia},
 url          = {en.wikipedia.org/wiki/Perfect_number},
)
@book(pollack,
 author       = {Paul Pollack},
 year         = {2009},
 title        = {Not Always Buried Deep: A Second Course in Elementary Number Theory},
 publisher    = {American Mathmatical Society},
)
@book(robinson,
 author       = {Abraham Robinson},
 year         = {1966},
 title        = {Non-Standard Analysis},
 publisher    = {North-Holland Publishing Co.},
)