Curt Hofemann, curt_hofemann@@yahoo.com, in a post-em, gives another source for Robert III:
FYI, ES XIV:136 shows: Seigneur (dominus) de Vitre (my notes aren't the best but ES may have said "Herr" not Seigneur & I translated, dominus=Latin meaning master, lord, sir, which in French would be Seigneur) death: vor 1184 (11.XI 1173) (before 1184 possibly 11 Nov 1173) buried: Abbey of Savigny