On Marcus Iunius Brutus (85? – 42 BC), leader on the conspiracy against Caesar in 44, see the biographical sketch by Badian 2003, and the exhaustive overview by Gelzer 1918; on the historical figure and its posterity see Clarke 1981; on Cicero and Brutus still useful is Boissier 1888: 321-379; other references listed in Garbarino 2003: 91.
According to the 4th-century AD grammarian Nonius, the collection (hereafter referred to as MBrut) originally numbered at least 9 books; the 15 surviving fragments (12 from unidentified books) are edited by Watt 1958: 163-166. The manuscript tradition is the same as that of the Ad Quintum Fratrem collection for the …
Prost, François. "Epistulae ad Marcum Brutum". The Literary Encyclopedia. First published 29 July 2012
[https://www.litencyc.com/php/sworks.php?rec=true&UID=34667, accessed 21 January 2019.]