Spinors: a Mathematica package for doing spinor calculus in General   Relativity
  The "Spinors" software is a "Mathematica" package which implements 2-component spinor calculus as devised by Penrose for General Relativity in dimension 3+1. The "Spinors" software is part of the "xAct" system, which is a collection of "Mathematica" packages to do tensor analysis by computer. In this paper we give a thorough description of "Spinors" and present practical examples of use. 
Alfonso Garc\'ia-Parrado G\'omez-Lobo and Jos\'e M. Mart\'in-Garc\'ia
gr-qc hep-th