[snip the words of the ineducable lying psychopathic troll  Schwartz]

Schwartz explicitly demonstrates that he is completely ignorant of
of the axioms of a vectr space.  He has no concept of an axiom or what a 
vector is.  Consider his relativistic drool and dribble:

  tau = (t- vx/c^2) * gamma,
  x' = x - vt,
  xi = x' * gamma.
  eta = y,
  zeta = z.

His refusal to accept that t must have an additive inverse to be an 
element  of vector springs from a massive empirical stupidity re vector 
spaces.
This is particularly vital when it comes to defining velocity as the 
vector quantity dx/dt,
For
  d(xi)/d(tau) =   d(x- dx/dt . t)  / d(t-dx/dt . (x /c^2) ) =/= dx/dt.


Thus the PoR is violated, the velocity of B with respect to A  is not 
the velocity of A with respect to B.

[snip crap]

Androcles.