Modern Hagiography
Dictionary of Saintly Women (one of 12 by this name, that of Diessen, see Butler below, is no. 6)
Lives of the Saints by Alban Butler. (10 April, mentions both Hackeborn and Diessen, not sure which one she actually is, as Saint Mechtilde of Hackeborn has no connection to Diessen)
Miniature Lives of the Saints for Every Day in the Year (10 April)
La vie des saints (6 July)
Legends of the Blessed Sacrament Gathered from the History of the Church and the Lives of the Saints by Emily Mary Shapcote.
Medieval Hagiography
BHL, Supplement (19 November, of Diessen is 30 May)
Writings by Saint Mechthilde
Love of the Sacred Heart Illustrated by Saint Mechtilde
Art & Architecture
Lives and Legends of the English Bishops and Kings, Mediaeval Monks, and Other Later Saints by Mrs. Arthur Bell.
Nihil sub sole novum 
