^Galileo Galilei: Siderius Nuncius, Venice, 1610. English Translation published at Bard College, Hudson NY" October 9, 2003 English Translation[1] （页面存档备份，存于互联网档案馆） Original Latin version[2] （页面存档备份，存于互联网档案馆）
^Tom Pope and Jim Mosher: Galilean telescope homepage" March 17, 2006 存档副本. [2008-01-30]. （原始内容存档于2008-01-30）., "Some have expressed puzzlement that in his text Galileo does not mention the nebulosity (known in modern nomenclature as M42) enveloping these stars. ... Galileo believed, as he explains in Sidereus Nuncius, that what looks nebulous to the eye is resolved into stars by his telescope; what looks nebulous through his telescope could presumably also be resolved into stars by a still larger and more powerful telescope. Hence, a diffuse glow would be, more than anything, an indication of the limitations of his telescope and not particularly worthy of special note."
^ Tom Pope and Jim Mosher: Page on Galileo's February 4, 1617 notebook drawing of the Trapezium region, May 2, 2006 "Perhaps significantly, Galileo makes no mention of having noticed the now well-known gas cloud, M42, surrounding the Trapezium stars."[3]互联网档案馆的存檔，存档日期2011-08-11.
