Referencias de la Web

- http://www.westburyontrymmethodistchurch.org.uk/site/files/group-people-silhouette.jpg
- http://www.southasianconcern.org/images/sac_photos/prayer_room/man_silhouette.jpg
- http://2.bp.blogspot.com/_ZeeLp9OkVRA/S-mTnfARDcI/AAAAAAAAPPM/3PQaYKbSGQw/s1600/duda.jpg
  Semiestructurada: http://isimus2math.files.wordpress.com/2009/07/examen.gif
- http://i1.calameoassets.com/100303024436-f6db122df866133e98f092285d60deb5/thumb.jpg