Where does the saying "Quod licet Jovi non licet bovi" come from? My Google research was not satisfactory. Any book or article you know of that can guide me?
There is a Wikipedia article on that phrase. If it is to be trusted, the first known occurrence is in Aus dem Leben eines Taugenichts (1826) by Joseph Freiherr von Eichendorff. The phrase can indeed be found in the novel; see chapter 9 or search for the phrase.
Terence had a similar phrase, but not quite the same: Aliis si licet, tibi non licet. Cicero also writes: aliud bovi, aliud homini. I think it is fair to say that the thought is ancient and known to the Romans, but the exact wording seems to be much more recent.