http://web.telia.com/~u51102888/anims/alpha1/alpha1.htm
http://qesnrecit.qc.ca/ccdb/2mmclub/tips5.php
http://education-world.com/a_lesson/lesson299.shtml
http://papeldeparede.weblog.com.pt/arquivo/2004_09.html
http://geocities.com/TelevisionCity/9147/midi.html