Sources

1) Source: MRS CHRISTIAN SMITH'S DOCUMENTS "Parties: 1) Dame Isabel, widow of Sir Gerard de Usflet". Dated: 16 July 1351. External Link
https://www.eastriding.gov.uk/CalmView/Record.aspx?src=CalmView.Catalog&id=zDDCS%2f25%2f6. Reference: DDCS/25/6 (Data from secondary evidence)
2) Source: Court of Common Pleas: Plea Rolls "Dame and later Dowager Isabella de Usflet, a wife of the first Sir Gerard de Usflete and mother of the second one, also grandmother of the third one," Dated: 1411. External Link
https://discovery.nationalarchives.gov.uk/details/r/C318241. Reference: CP 40/601 (Data from direct source)
3) Source: Savile of Rufford: Deeds and Estate Papers "Chirograph: Marriage settlement - Henry de Nuhill clerk to Brian of Thornhill on marriage of Gerald son of Gerard de Ufflet and Margaret daughter of Brian, lands etc in Swanland and Ufflet."Dated: 1357-1368. Reference: DD/SR/209/124 (Data from direct source)
4) Source: The History of Parliament . External Link
http://www.historyofparliamentonline.org/volume/1386-1421/member/usflete-sir-gerard. Reference: Usflete, Sir Gerard, of North Ferriby and Ousefleet, Yorks. (Questionable reliability of evidence)
5) Source: MRS CHRISTIAN SMITH'S DOCUMENTS "Parties: 1) Gerard de Usflet". Dated: 8 March 1350. External Link
https://www.eastriding.gov.uk/CalmView/Record.aspx?src=CalmView.Catalog&id=zDDCS%2f25%2f5. Reference: DDCS/25/5 (Data from direct source)
6) Source: The History of Parliament . External Link
http://www.historyofparliamentonline.org/volume/1386-1421/member/beauchamp-sir-william-1421. Reference: Beauchamp, Sir William (d.c.1421), of Powick, Worcs. and Alcester, Warws. (Unreliable evidence or estimated data)
7) Source: Special Collections: Ancient Petitions "Petitioners: Katherine Beauchamp, wife of William Beauchamp; William Bekwith (Beckwith); Joan Beckwith, wife of William Bekwith; Thomas Busoigne; Anne Busoigne, wife of Thomas Busoigne; Robert Haldenby; Isabella Haldenby, wife of Robert Haldenby...Nature of Request: The petitioners, as heirs of Gerard Ufflete, request their rights in his lands, occupied by the duchess of Norfolk."Dated: 1416-1425. External Link
http://discovery.nationalarchives.gov.uk/details/r/C9295320. Reference: SC 8/189/9442 (Data from direct source)
8) Source: Testamenta eboracensia; or, Wills registered at York The will of Gerard de Usflete dated 5 September 1405 and proved 5 April 1406. (Questionable reliability of evidence)