Rujukan WikiPedia: Astronomi sinar-X http://heasarc.gsfc.nasa.gov/docs/heasarc/headates... http://heasarc.gsfc.nasa.gov/cgi-bin/Tools/high_en... http://www.wikisky.org/ http://www.astronomycast.com/astronomy/ep-135-x-ra... http://imagine.gsfc.nasa.gov/ https://www.wikidata.org/wiki/Q1852#identifiers https://d-nb.info/gnd/4050311-2 http://uli.nli.org.il/F/?func=find-b&local_base=NL... https://id.loc.gov/authorities/subjects/sh85148728 https://id.ndl.go.jp/auth/ndlna/00561916
