Liên kết ngoài Tinh_vân_Lưỡi_liềm

Thiên thể NGC 6500 đến 6999

Tài liệu tham khảo

WikiPedia: Tinh_vân_Lưỡi_liềm http://jumk.de/astronomie/big-stars/wr-136.shtml http://chandra.harvard.edu/photo/2003/ngc6888/ http://www.noao.edu/image_gallery/html/im0834.html http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=... http://www.ngcicproject.org/ngcicdb.asp http://server1.wikisky.org/starview?object=Tinh+v%... http://www.wikisky.org/?object=Tinh+v%C3%A2n+L%C6%... http://www.wikisky.org/?object=Tinh+v%C3%A2n+L%C6%... http://www.wikisky.org/?object=Tinh+v%C3%A2n+L%C6%... http://www.wikisky.org/?object=Tinh+v%C3%A2n+L%C6%...