http://palillo.usach.cl

http://www.algebra-online.com

http://www.sosmath.com/matrix/matrix.html

http://www.sercomtel.com.br/matematica

http://ww9.zaz.com.br/matematica/arq12.htm

http://www-history.mcs.st-and.ac.uk/history/HistTopics/Matrices_and_determinants.html