Modern Hagiography
Miniature Lives Of The Saints For Every Day In The Year by Henry Sebastian Bowden.
Medieval Hagiography
Barbara Newman, Thomas of Cantimpré: The Collected Saints’ Lives: Abbot John of Cantimpré, Christina the Astonishing, Margaret of Ypres, and Lutgard of Aywières (2008) (not in the public domain).
The Writings of Saint Lutgardis
The Heavenly Court of the Holy Cistercian Nun Saint Lutgarde of Brabant
Art & Architecture
Dream of Lutgardis on Charles Bridge in Prague
Warburg Institute Iconographic Database
Post-Biblical Saints Art Index
The Saints in Art by Joseph Maria von Radowitz.
Emblems of Saints by Which They Are Distinguished in Works of Art by F. C. Husenbeth.
Nihil sub sole novum 
