The Lorentz Velocity Transformations defining velocities as: u x = dx/dt, u y = dy/dt, u' x = dx'/dt', etc. it is easily shown that: With similar relations. - ppt download
If speed exceeds that of light, time becomes imaginary in the Lorentz transformation, what does that imply? - Quora
Consequences of the Lorentz transformations
The Lorentz transform equations, the addition of velocities and spacetime