Note: Sheffield's involvement with Leicester possibly began as an affair during the 1570s; however Sheffield claimed a private marriage occurred at Leicester's house at Esher, Surrey between 11 Nov. and 25 Dec. of this year
The Complete Peerage of England, Scotland, Ireland, Great Britain, and the United Kingdom. 1887–98 (8 vols); 1910–59 (13 vols). 6 vols. Gloucester: Alan Sutton, 1982.
Oxford Dictionary of National Biography. 01/05/2005 (http://www.oxforddnb.com)