MEXICO AND SOUTH AMERICA

http://hanksville.phast.umass.edu/yucatan/mayamath.html

Includes info about the number system of the Mayas.

http://ce-atl.postgrado.unam.mx/matrix/serie02/cuad02-

Aztec calendar

http://www.xs4all.nl/~voorburg/aztec.html

Aztec calendar