@article{10_4171_dm_33,
     author = {Udo Hertrich-Jeromin},
     title = {Supplement on curved flats in the space of point pairs and isothermic surfaces: {A} quaternionic calculus},
     journal = {Documenta mathematica},
     pages = {335--350},
     year = {1997},
     volume = {2},
     doi = {10.4171/dm/33},
     url = {http://geodesic.mathdoc.fr/articles/10.4171/dm/33/}
}