On Timelike and Spacelike Developable Ruled Surfaces
  In this study, we have obtained the distribution parameter of a ruled surface generated by a straight line in Frenet trihedron moving along a timelike curve and also along another curve with the same parameter. At this time, the Frenet frames of these timelike curves are not the same. We have moved the director vector of the first curve along the second curve. It is shown that the ruled surface is developable if and only if the base timelike curve is helix. In addition, some smilarities and differences are presented with theorems and results. 
Yusuf Yayli, Semra Saracoglu
math.DG