Friends, I am studying the Raychaudhuri Equation. But Landau also deduced this equation, in independent way. What necessary to know it is: in which Landau workmanship made the study that resulted in today known as Landau-Raychaudhuri Equation? I thank since already any information the respect. They forgive me the English. I am Brazilian and I do not write very in English. Victorneto.