Tài liệu tham khảo WikiPedia: NGC 2170 http://cseligman.com/text/atlas/ngc21a.htm#2170 http://nedwww.ipac.caltech.edu/cgi-bin/nph-objsear... http://simbad.u-strasbg.fr/simbad/sim-id?Ident=NGC... http://www.seds.org/~spider/ngc/ngc.cgi?NGC2170 https://www.webcitation.org/6ZtHYJQEM?url=http://c...
