Reference

	1000+ The Amateur Astronomers Field Guid to Deep Sky Observing by Tom Lorengin, Tim Sechler Year: 1987 Hits: 3823 Date insert: Monday, 31 December 2018
	101 Objects to See in the Night Sky by Robin Scagell Year: 2014 Hits: 4048 Date insert: Monday, 31 December 2018
	A Complete Manual of Amateur Astronomy by P. Clay Sherrod Year: 1981 Hits: 3773 Date insert: Monday, 31 December 2018
	Astronomers Computer Companion by Jeff Foust, Ron LaFon Year: 1999 Hits: 3887 Date insert: Monday, 31 December 2018
	Astronomical Almanac for the Year 2020 by Unknown NA Year: 2019 Hits: 4446 Date insert: Monday, 31 December 2018