Bibliography on Hilbert's Tenth Problem  liinwww.ira.uka.de/bibliography/Math/Hilbert10.html Searchable, 400 items.

Diagonal Quartic Surfaces  www.boojum.org.uk/maths/quartic-surfaces Articles, computations and software in Magma and GP by Martin Bright.

Diophantine Geometry in Characteristic p  www.ma.utexas.edu/users/voloch/surveylatex/surveylatex.html A survey by José Felipe Voloch.

Diophantine m-tuples  www.math.hr/~duje/dtuples.html Sets with the property that the product of any two distinct elements is one less than a square. Notes and bibliography by Andrej Dujella.

Egyptian Fractions  www.ics.uci.edu/~eppstein/numth/egypt Lots of information about Egyptian fractions collected by David Eppstein.

The Erdos-Strauss Conjecture  math.uindy.edu/swett/esc.htm The page establishes that the conjecture is true for all integers. Tables and software by Allan Swett.

Hilbert's Tenth Problem  logic.pdmi.ras.ru/Hilbert10 Statement of the problem in several languages, history of the problem, bibliography and links to related WWW sites.

Hilbert's Tenth Problem  www.ltn.lv/~podnieks/gt4.html Given a Diophantine equation with any number of unknowns and with rational integer coefficients: devise a process, which could determine by a finite number of operations whether the equation is solvable in rational integers.

Linear Diophantine Equations  www.thoralf.uwaterloo.ca/htdocs/linear.html A web tool for solving Diophantine equations of the form ax + by = c.

Pell's Equation  www.ieeta.pt/~tos/pell.html Record solutions.

Pell's Equation  www-history.mcs.st-andrews.ac.uk/history/Projects/Pearce/Chapters/Ch8_… Provides information on this equation, solved by Brahmagupta in 628 AD.

Pythagorean Triples Etc.  www.pythag.net A web text by Fred Barnes on 60-, 90-, and 120-degree integer-sided triangles.

Pythagorean Triples in JAVA  www.hbnweb.de/pythagoras/pythagoras.html A JavaScript applet which reads a and gives integer solutions of a^2+b^2 = c^2.

Pythagorean Triplets  www.hbmeyer.de/pythagen.htm A Javascript calculator for pythagorean triplets.

Quadratic Diophantine Equation Solver  www.alpertron.com.ar/QUAD.HTM Dario Alpern's Java/JavaScript code that solves Diophantine equations of the form Ax^2 + Bxy + Cy^2 + Dx + Ey + F = 0 in two selectable modes: "solution only" and "step by step" (or "teach") mode. There is also a link to his description of the solving methods.

Rational and Integral Points on Higher-dimensional Varieties  aimath.org/WWN/qptsurface2 Some of conjectures and open problems, compiled at AIM.

Rational Triangles  grail.cba.csuohio.edu/~somos/rattri.html Triangles in the Euclidean plane such that all three sides are rational. With tables of Heronian and Pythagorean triples.

Thue Equations  finanz.math.tu-graz.ac.at/~cheub/thue.html Definition of the problem and a list of special cases that have been solved, by Clemens Heuberger.