By March 1903 Einstein had changed his mind. Indeed, a letter to Besso contains some of the central ideas of the 1905 dissertation. Kleiner was, of course, one of the two faculty reviewers of the dissertation, submitted by Einstein to the University on 20 July 1905. Kleiner's judgement of the dissertation was very positive: "the arguments and calculations to be carried out are among the most difficult in hydrodynamics." The other reviewer, Heinrich Burkhardt, Professor for Mathematics at the University, added: "the mode of treatment demonstrates fundamental mastery of the relevant mathematical methods."