Sources

1) Source: Main Ferrers Estate "Consists of...Copy of a writ of Non Omittas for...husband of Elizabeth, dau. of Thomas the brother of John Bermyngham for possession of property...for possession for Edmund son of Robert."Dated: 1425-1425. External Link
http://discovery.nationalarchives.gov.uk/details/r/abccbe0f-d255-450a-96c1-4b8f1c211d67. Reference: 26D53/1584 (Data from direct source)
2) Source: Chancery: Inquisitions Post Mortem, Series I, Edward III "JOHN DE FERRARIIS, knight...He died on 31 March, 41 Edward III. Robert de Ferrariis, his son, aged 7 years and more, is his heir...Broghton. The manor, held in right of Elizabeth his wife, who survives. Elizabeth holds it for life as jointly enfeoffed with one Fulk Lestrange, her former husband, deceased, the reversion belonging to the heirs of John Lestrange, father of Fulk. The manor is not held of the king, but of whom else it is held the jurors know not.He died on 3 April last. Robert, son of the aforesaid John and Elizabeth, aged 7 years and more, is his heir." Date: 1367. External Link
https://www.british-history.ac.uk/inquis-post-mortem/vol12/pp105-118. Reference: C 135/193/13 (Data from secondary evidence)
3) Source: Varied - Secondary Source for Medieval Genealogy "...I identified Margaret Ferrers, wife of John Beauchamp, as the daughter of Edmund Ferrers, 6th Lord Ferrers, of Chartley, co. Stafford, in the book, Plantagenet Ancestry, 2nd edition, by David Faris, pp. 138, 216. This identification was made based on the following information:1. Margaret (Ferrers) Beauchamp named her brother, Richard Ferrers, in her PCC will proved in 1488. For an abstract of Lady Margaret's will, see the book, Testamenta Vetusta.2. Reviewing the high born Ferrers families of this period, I determined that Edmund Ferrers, 6th Lord Ferrers, of Chartley (died 1435), had a younger son named Richard who would fit chronologically to be Margaret's brother.3. I went through the published Patent and Close rolls of this period. I found that Margaret's husband, John Beauchamp, served as a feoffee in 1442 for William Ferrers, Knt., of Chartley, eldest son of Edmund Ferrers. This would be what what one would expect to find if Margaret was Edmund's daughter, as feoffees were often close relatives. Conversely, if John Beauchamp had no connection with the Chartley family, it would be difficult to explain his appearance as a feoffee for the Ferrers family of Chartley.4. Margaret Ferrers was evidently named for Edmund Ferrers' mother, Margaret (Despencer) Ferrers...". External Link
https://groups.google.com/g/soc.genealogy.medieval/c/l5gehH_lLd0. Reference: Post by Douglas Richardson dated 16 July 2001 to soc.genealogy.medieval (Questionable reliability of evidence)
4) Source: Chancery: Inquisitions Post Mortem, Series I, Henry VI "Ferrers, Edmund, kt, of Charteley: Northants, Glos, London, Oxon, Berks, Staffs, Derb, Hunts, Som, Warw""He died on 17 December last. William Ferrers, esquire , his son and next heir, is aged 23 years and more."Dated: Jan 1436. External Link
http://discovery.nationalarchives.gov.uk/details/r/C6159460. Reference: C 139/75/33. King's College London, 2014. | Mapping the Medieval Countryside [online]. Available at http://www.inquisitionspostmortem.ac.uk/view/inquisition/24-480/483 (Data from secondary evidence)