Reference

	The Year-Round Messier Marathon Field Guide: With Complete Maps, Charts and Tips to Guide You to Enjoying the Most Famous List of Deep-Sky Objects by H. C. Pennington Year: 1997 Hits: 7611 Date insert: Monday, 31 December 2018
	Through the Telescope: A Guide for the Amateur Astronomer by Michael R. Porcellino Year: 1989 Hits: 4503 Date insert: Monday, 31 December 2018
	Through The Telescope: A Guide For The Amateur Astronomer (Revised and Updated Edition) by Patricia Barnes-Svarney Year: 1999 Hits: 4403 Date insert: Monday, 31 December 2018
	Touring the Universe through Binoculars: A Complete Astronomers Guidebook by Heather T. Cameron, Gabriele Vanin Year: 1990 Hits: 4522 Date insert: Monday, 31 December 2018
	Undiscovering the Secrets of the Red Planet by Matt Golombek Year: 1998 Hits: 5483 Date insert: Monday, 31 December 2018