Tài liệu tham khảo WikiPedia: NGC_281 http://deepspacemap.com/#?l=56.6043,166.7658,9 http://nedwww.ipac.caltech.edu/ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bi... http://adsabs.harvard.edu/cgi-bin/nph-bib_query?db... http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=... http://apod.gsfc.nasa.gov/apod/ap050823.html //arxiv.org/abs/1407.1609 //doi.org/10.1086%2F190049 //doi.org/10.1088%2F0004-637X%2F790%2F2%2F99 http://www.wikisky.org/?ra=0.88161111111111&de=56....
