I can cite a number of references [by church historians] that refute Voerman's research.  They are:

1) Mary Ann Rossi, "Priesthood, Precedent, and Prejudice: On Recovering the Women Priests of Early Christianity" Journal of Feminist Studies in Religion 7 [1991] pp. 72-93

2) Haye van de Meer, WOMEN PRIESTS IN THE CATHOLIC CHURCH: A THEOLOGICAL-HISTORICAL INVESTIGATION [Philadelphia: Temple University Press, 1973].

When Benedictine abbesses held episcopal authority until 1873

4] Elizabeth Connor, "The Royal Abbey of Las Huelgas and the Jurisdicton of its Abbesses," Cistercian Studies, 23 [1988] pp. 128-55.

5) F. Donald Logan, A HISTORY OF THE CHURCH IN THE MIDDLE AGES [London: Routeledge, 2002].

6) Ida Raming, THE PRIESTLY OFFICE OF WOMEN: GOD'S GIFT TO A RENEWED CHURCH [New York: Scarecrow Press, 2004]

6) Gary Macy, THE HIDDEN HISTORY OF THE ORDINATION OF WOMEN [New York: Oxford University Press, 2007.