$(1,2)$-Null Bertrand Curves in Minkowski Spacetime
  In this paper we study null Bertrand curves in $R_{1}^{4}$ under the assumption the curve has a Cartan frame. We show that if the derivative vectors of the null Cartan curve in $R_{1}^{4}$ is linearly independent, then this curve is not a Bertrand curve. Since then the already known notion of null Bertrand curves in $R_{1}^{4}$ occurs only if the derivative vectors of the curve is linearly dependent. We will introduce an idea of Bertrand curves and abiding by this idea we bring to light under which conditions a null Cartan curve in $R_{1}^{4}$ is a Bertrand curve. 
Mehmet G\"o\c{c}men and Sad{\i}k Kele\c{s}
math.DG