Formulas for direct determination of real speed in Galactic superluminal   sources
  In this paper we show explicit and direct relations between the expected quantities and the observed quantities for the components of Galactic superluminal sources. Basic formulas for calculating the real speed and the angle to the line of sight of the components from the data of proper motions and the distance of the source are presented. We point out that the real speed and the angle to the line of sight of components can be uniquely and directly determined from the observed values of the proper motions and the distance of the source. It is not necessary to calculate an intermediate quantity first and then using the resulted value to calculate the two required quantities. The process of the calculation is simple, and in this way, some extra uncertainties are avoided. 
Yi-Ping Qin