Barack Obama

http://www.biography.com/people/barack-obama-12782369
http://es.wikipedia.org/wiki/Barack_Obama

George W. Bush

http://www.biography.com/people/george-w-bush-9232768
http://www.history.com/topics/us-presidents/george-w-bush

George H. W. Bush

http://www.biografiasyvidas.com/biografia/b/bush.htm
http://www.history.com/topics/us-presidents/george-bush

http://millercenter.org/president/bush

William J. Clinton

http://www.biografiasyvidas.com/biografia/c/clinton.htm
http://www.let.rug.nl/usa/biographies/bill-clinton/
http://www.proyectosalonhogar.com/us_presidents/clinton.htm

Ronald Reagan

http://es.wikipedia.org/wiki/Ronald_Reagan

https://www.whitehouse.gov/1600/presidents/ronaldreagan

http://www.biografiasyvidas.com/biografia/r/reagan.htm

Jimmy Carter

http://es.wikipedia.org/wiki/Jimmy_Carter
https://www.whitehouse.gov/1600/presidents/jimmycarter
http://www.cartercenter.org/news/experts/jimmy_carter.html

http://www.biografiasyvidas.com/biografia/c/carter_jimmy.htm

Gerald Ford

http://www.biography.com/people/gerald-ford-9298683

http://es.wikipedia.org/wiki/Gerald_Ford

http://www.fordlibrarymuseum.gov/grf/fordbiop.asp