Charakterisierungen spezieller windschiefer Regelfl\"achen durch die   Normalkr\"ummung ausgezeichneter Fl\"achenkurven
  We consider ruled surfaces in the three-dimensional Euclidean space and some geometrically distinguished families of curves on them whose normal curvature has a concrete form. The aim of this paper is to find and classify all ruled surfaces with the mentioned property 
Stylianos S. Stamatakis
math.DG