See S.R. Johnson, 'Cheke, John (1514-57), of Cambridge and London', in S.T. Bindoff (ed.), The History of Parliament: the House of Commons 1509-1558 (Secker & Warburg, 1982), History of Parliament online. The Pirgo connection stated by P.W. Hasler in 'Cecil, Thomas (1542-1623), of Burghley House, Lincs. and Wimbledon, Surr.', in P.W. Hasler (ed.),
The History of Parliament: the House of Commons 1558-1603 (from Boydell & Brewer, 1981), History of Parliament online does not appear in other sources until a later generation.
oxforddnb.com
R. Milward, 'Cecil, Thomas, first earl of Exeter (1542-1623)', Oxford Dictionary of National Biography (2004). ODNB Link