^Galileo Galilei: Siderius Nuncius, Venice, 1610. English Translation published at Bard College, Hudson NY" October 9, 2003 English Translation[1] （頁面存檔備份，存於網際網路檔案館） Original Latin version[2] （頁面存檔備份，存於網際網路檔案館）
^Tom Pope and Jim Mosher: Galilean telescope homepage" March 17, 2006 存档副本. [2008-01-30]. （原始內容存檔於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]網際網路檔案館的存檔，存檔日期2011-08-11.
