Webgrafia

http://www.xtec.cat/~rmolins1/univers/cat/galaxies.htm
http://www.xtec.cat/~jjimen18/galaxies.htm
http://www.jouscout.com/astro/galaxies.htm


http://www.astromia.com/universo/vialactea.htm
https://ca.wikipedia.org/wiki/Formaci%C3%B3_i_evoluci%C3%B3_de_les_gal%C3%A0xies

https://cat.elpais.com/cat/2015/09/08/ciencia/1441724008_517820.html
http://www.atlasoftheuniverse.com/catala/startype.html