Gregorius (c. 1190), Hartmann von Aue’s story of sin and grace, is probably the most discussed medieval German work. Its double incest, a universal taboo, continues to fascinate readers and avoid classification. Although the Oedipus myth was known in the Middle Ages, it has little similarity with this Christian text that examines the social and ethical ramifications of incest within an Augustinian framework. Hartmann probably used versions of the twelfth-century French saint’s legend La vie du pape Grégoire to build his creative reinterpretation. A re-evaluation for a modern audience, Der Erwählte (1951), has been written by Thomas Mann.
Dobozy, Maria. "Gregorius". The Literary Encyclopedia. First published 31 March 2005
[https://www.litencyc.com/php/sworks.php?rec=true&UID=13998, accessed 18 February 2018.]