@InProceedings{GPU05,
author    = {Ingo Ginkel and J{\"o}rg Peters and Georg Umlauf},
title     = {On normals and control nets},
booktitle = {Mathematics of Surfaces XI},
year      = 2005,
publisher = {Springer-Verlag},
editor    = {R.~Martin and H.~Bez and M.~Sabin}
pages     = {233-239}
}