http://www.fortunecity.com/skyscraper/deschutes/745/id38.htm

http://sweet.ua.pt/~fmart/index.html?2002

http://educar.sc.usp.br/matematica/m4p2t4.htm

http://educar.sc.usp.br/matematica/l2t7.htm  

http://conhecimentosgerais.hypermart.net/matematica/aritmetica-e-sistemas-numericos.shtml

http://athena.mat.ufrgs.br/~portosil/passeio.html

http://www.aritmi.hpg.ig.com.br//    

http://www.olejarz.com/arted/perspective

http://www.designs4the.net/Area_51/Virtual_Gallery/Vanishing_Point/vanishing_point.html