Estas imagenes han sido sacadas de
 http://xora.org/2011-evitar-violaciones-de-derecho-de-autor-copyright-%C2%BFque-es-y-%C2%BFpara-que-sirve/

http://institutomexicocomputacion.wordpress.com/2012/09/03/copyright-class-homework/

ttp://en.wikipedia.org/wiki/Copyright_Term_Extension_Act

http://fraterneo.blogspot.com/2010/12/que-es-el-copyleft.html

http://www.pateandopiedras.net/2010/11/nacimiento-del-copyright-y-censura-contra-el-mito-de-los-origenes-liberal/

http://xochipilli.wordpress.com/2010/05/03/k-maleon-culturalibre/

http://katalystnetwork.com/vs/singularity/