De virginitate, in one book, was written in defense of the earlier treatise DE VIRGINIBUS. Paragraphs 14-23 are thought to be interpolated (see Machielsen, CPPM IIB.3575). The work titled De virginitate in the Anglo-Saxon manuscripts is in fact De virginibus (on the confusion of the titles, see the entry for De virginibus), followed by DE VIDUIS then by De virginitate which is identified in the Oxford manuscripts as "liber IIII" of "de virginibus" (see Nazzaro 1981 pp 116-17). In the Cambridge manuscript De virginitate is without title or rubric, but is distinguished from De viduis by a space and an enlarged initial capital (information from Thomas N. Hall). The entry "Ambrosius De virginitate" in the Peterborough booklist may have referred to a manuscript containing DE VIRGINIBUS, possibly combined with De viduis and De virginitate and some or all of the other works which often circulated together as part of a corpus of Ambrosian works on virginity (for details see under De virginibus