https://in-the-sky.org/data/catalogue.php?cat=Messier&const=1&type=SNR&sort=0&view=0
The Messier objects - In-The-Sky.org
messier objectssky
https://www.bullmoose.com/p/17232554/notwist-messier-objects
Notwist Messier Objects | Bull Moose
Notwist:Messier Objects,CD,ROCK
messier objectsbullmoose
https://www.brighthub.com/science/space/articles/58807/
Facts About the Messier Objects Catalog
When Charles Messier was looking for comets, he came across other objects that had similar characteristics, but were not comets. He decided to create a catalog...
facts aboutmessier objectscatalog