Henry VI, Part 1

Here is a list of definite, probable and possible sources for 1 Henry VI:

The Union of the Two Noble and Illustre Famelies of Lancastre and Yorke by Edward Hall
The Chronicles of England, Scotland and Ireland by Raphael Holinshed
Historia Regum Britanniae by Geoffrey of Monmouth
Journal of the Siege of Rouen by Sir Thomas Coningsby

For further information, see: Bullough, Geoffrey. Narrative and Dramatic Sources of Shakespeare, Volume III: Earlier English History Plays. London: Routledge and Kegan Paul, 1975.

Henry VI, Part 1 - Sources