 Unsolved Problems in Number Theory, Logic, and Cryptography  Tim Roberts
This site "concentrates only on problems which are easily understandable to the amateur.... explainable on a single screen (perhaps 200 words), using simple terminology." Read brief descriptions of open problems such as the Chromatic Number, the Collatz
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 The Virtual Mathematics Center  Martindale's Graduate & Undergraduate Center
Preprints and online journals from a wide variety of math and science organizations; Online math dictionaries and encylopedias; mathematics courses, tutorials and databases; courses by subject; related mathematics information and databases.
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 Wavelet Resources  Mathematics Dept., Yale University
Preprints and software for wavelets available from the Yale Mathematics Department.
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 The Work of Robert Langlands  Mathematics Dept., University of British Columbia, Canada
A selection from Langlands' professional correspondence, previously unpublished work, and published work now out of print. Thesis, papers, manuscripts, letters, and bibliography.
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 XNumber World  James Redin
With the Extended Numerical Keyboards with Structured DataEntry Capability method, enter a number in the same way as you think on the number; for example, input one million and fiftyseven with the four keystrokes 1, million, 5, and 7, in that order.
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 Zen Calculus: A Short, Easy Introduction to Calculus  Peter McCauley
An 11page PDF file that establishes the fundamentals of calculus without using infinite series or limits. Suitable for high school students with one year of algebra.
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