http://www.mars-one.com/faq/mission-to-mars/why-mars-and-not-another-planet
https://en.wikipedia.org/wiki/Proxima_Centauri_b
https://www.nasa.gov/ames/kepler/kepler-186f-the-first-earth-size-planet-in-the-habitable-zone
http://listogre.com/facts/science/top-10-earth-like-planets/
http://www.space.com/18790-habitable-exoplanets-catalog-photos.html
http://www.space.com/16728-top-5-habitable-alien-planets-countdown.html
http://www.wonderslist.com/10-most-potentially-habitable-planets/
http://www.space.com/24142-kepler-62f.html
http://www.solarsystemquick.com/universe/gliese-667cc.htm
https://en.wikipedia.org/wiki/Gliese_581g
https://en.wikipedia.org/wiki/Gliese_832_c