The parallel frame of a curve is an alternative approach to defining a moving frame. In this paper, we express the parallel frames of timelike and spacelike curves in a Minkowski space.
"Parallel Frames of Non-Lightlike Curves." Missouri J. Math. Sci. 20 (2) 127 - 137, May 2008. https://doi.org/10.35834/mjms/1316032813