@article{articleae5e6707,
title   = {The minimal number of roots of surface mappings and quadratic},
author = {Bogatyi, Semeon A. and Gonçalves, Daciberg Lima and Zieschang, Heiner},
year = {2001},
doi = {10.1007/s002090100203},
journal   = {Mathematische Zeitschrift}
}