@article{GDZPPN002301725,
title = {On the Distortion of Conformal Immersions between 2-Space Forms.},
journal = {Mathematische Annalen},
volume = {180},
year = {1969},
pages = {159-168},
zbl = {0172.46501},
url = {http://dml.mathdoc.fr/item/GDZPPN002301725}
}
HELFENSTEIN, H.G. On the Distortion of Conformal Immersions between 2-Space Forms.. Mathematische Annalen, Tome 180 (1969) pp. 159-168. http://gdmltest.u-ga.fr/item/GDZPPN002301725/