Reference

	Venus by E. C. Krupp, Gerald North Year: 2002 Hits: 4531 Date insert: Monday, 31 December 2018
	Webb Society Deep Sky Observers Handbook: Volume 3. Open and Globular Clusters by Kenneth Glyn Jones, Peter I. Manly Year: 1980 Hits: 3992 Date insert: Monday, 31 December 2018
	Webb Society Deep Sky Observers Handbook: Volume 4. Galaxies by Kenneth Glyn Jones, Peter I. Manly Year: 1981 Hits: 6242 Date insert: Monday, 31 December 2018
	Webb Society Deep-Sky Observers Handbook Vol. 1 : Double Stars by Kenneth Glyn Jones Year: 1986 Hits: 4030 Date insert: Monday, 31 December 2018
	Webb Society Deep-Sky Observers Handbook Vol. 5 : Clusters of Galaxies by Kenneth Glyn Jones, Peter I. Manly Year: 1982 Hits: 3950 Date insert: Monday, 31 December 2018