Sources

1) Source: The Berkeley Estate "The prior has granted to Thomas an anniversary in full choir [etc.] for the souls of Maurice, Thomas's father, and Isabel his mother and, after their deaths, for the souls of himself, Joan his wife and Maurice their son"Date: 24 February 1308. External Link
http://discovery.nationalarchives.gov.uk/details/r/c8a0e990-6cf7-4ba2-9921-e4027898c8d6. Reference: BCM/A/1/19/29 (Data from direct source)
2) Source: The metrical chronicle of Robert of Gloucester Sir Richard fiz le rei - of wan we speke biuore - Gental man was inou - thei he were abast ibore - vor the erles doughter of wareine - is gode moder was - & is fader the king Ion - ... - Sire morrisse of berkeleye - weddede suththe bicas - is doghter and bighet on hire - the knight sir tomas - ... - Tuelf hundred in the gher of grace - it was & eightene. Reference: 10,626
3) Source: The Berkeley Estate "Thomas has granted to the priory the land which John Blunt held of him; and has also confirmed a rent of 24s. in the vill of B. . . [which was granted to them by?] Maurice de Berkeley his father...Witnesses: . . . son of Richard, Peter de Stintescumbe, Richard de Couele, Thomas de ..., Robert de Couele, Robert de la Planke, Hugh the baker (pistor),...". External Link
http://discovery.nationalarchives.gov.uk/details/rd/76d1a4d9-8c6f-4fe9-b690-4d5a91d7af58. Reference: BCM/A/1/67/2 (Data from direct source)
4) Source: Chancery: Inquisitions Post Mortem, Series I, Edward I "Maurice de Berkeley...Thomas his son, aged 30, is his next heir...Slinbrugg. The manor, held of Henry de Berkele, service unknown because it was given in free marriage to a predecessor of the said Maurice."Dated: 5 April 1281. External Link
https://www.british-history.ac.uk/inquis-post-mortem/vol2/pp230-238. Reference: C 133/28/11 (Data from direct source)
5) Source: English Baronies: a Study of Their Origin and Descent, 1086-1327. Reference: Pages 13-14: Berkeley (Questionable reliability of evidence)
6) Source: The Berkeley Estate "Maurice de Berkeley, son of Sir Thomas de Berkeley, and John de Berkeley, his brother. n.d.Maurice has inspected the charter of the lands and holding of la Homme at Bradeleye which his father has granted to John and his issue, and has confirmed it.". External Link
http://discovery.nationalarchives.gov.uk/details/rd/65c28798-2051-4e86-a846-c6a583fc49ed. Reference: BCM/A/1/52/4 (Data from direct source)
7) Source: Chancery: Inquisitions Post Mortem, Series I, Edward III "Maurice de Berkeleye, son of (Thomas) de Berkeleye late Lord of Berkeleye...Thomas, his son, aged 30 years and more, is his next heir."Dated: c February 1327. External Link
https://www.british-history.ac.uk/inquis-post-mortem/vol7/pp84-97. Reference: C 135/9/3 (Data from direct source)
8) Source: Chancery: Inquisitions Post Mortem, Series I, Edward II "Thomas de Berkeleye alias de Berkelee...Maurice his son, aged 40 and more, is his next heir."Dated: August 1321. External Link
https://www.british-history.ac.uk/inquis-post-mortem/vol6/pp198-203. Reference: C 134/71/2 (Data from direct source)