A nonstandard-analysis characterization of submanifolds in Euclidean space. Hertrich-Jeromin, Udo — 2001 Balkan Journal of Geometry and its Applications (BJGA)
On conformally flat hypersurfaces and Guichard's nets. Hertrich-Jeromin, Udo — 1994 Beiträge zur Algebra und Geometrie
Supplement on curved flats in the space of point pairs and isothermic surfaces: A quaternionic calculus. Hertrich-Jeromin, Udo — 1997 Documenta Mathematica
Remarks on the Darboux transform of isothermic surfaces. Hertrich-Jeromin, Udo; Pedit, Franz — 1997 Documenta Mathematica