Help is available at the University of Tennessee-Martin site http://www.utm.edu/research/primes/glossary/EuclideanAlgorithm.html. An interactive version of the Euclidean algorithm is available at http://www.math.umn.edu/~garrett/js/gcd.html. A biography of Euclid is at http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Euclid.html.

See http://unics.rrzn.uni-hannover.de/zzzzwg1/HPF-Kurs/HTMLHPFCourseNotesnode131.html.

My own text-based tiling program in C is at trom.c. A C program by Anthony Quas, University of Memphis, to output a tiling in postscript format is at tiles.c. An animation of the algorithm can be found at Christopher P. Mawata’s site http://www.utc.edu/~cpmawata/trominos/.

For information about the Fibonacci numbers see http://www.ee.surrey.ac.uk/Personal/R.Knott/Fibonacci/fib.html. Code at http://www.wwu.edu/~nmaylor/software simulates the spiral arrangements of seeds according to various rules. A biography of Fibonacci is found at http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Fibonacci.html.

See my own site growth.pdf.

A good explanation of public-key cryptology can be found at http://www.rsasecurity.com/rsalabs/faq/2-1-1.html. An introduction to public-key cryptography is at http://developer.netscape.com/docs/manuals/security/pkin/contents.htm.