A Comment on 'On the Rotation Matrix in Minkowski Space-time' by Ozdemir   and Erdogdu
  We comment on the article by M. Ozdemir and M. Erdogdu. We indicate that the exponential map onto the Lorentz group can be obtained in two elementary ways. The first way utilizes a commutative algebra involving a conjugate of a semi-skew-symmetric matrix, and the second way is based on the classical epimorphism from SL(2,C) onto SO_0(3,1) 
Arkadiusz Jadczyk and Jerzy Szulga
physics.gen-ph