A note on "Einstein's special relativity beyond the speed of light by   James M. Hill and Barry J. Cox"
  We show that the transformations J. M. Hill and B. J. Cox introduce between inertial observers moving faster than light with respect to each other are consistent with Einstein's principle of relativity only if the spacetime is 2 dimensional. 
Hajnal Andr\'eka, Judit X. Madar\'asz, Istv\'an N\'emeti, and Gergely   Sz\'ekely
gr-qc math-ph math.MP