As mentioned [here][1] the commentary attributed to [Rashi][2] on [Avot][3] may not have been authored by him.

This is stated by [R. Yaakov Emden][4] in the introduction to "Ets Avot".

Which other sources state that the commentary was not authored by him?


  [1]: https://judaism.stackexchange.com/questions/15520/which-masechtot-dont-really-have-rashi/15574#15574
  [2]: https://en.wikipedia.org/wiki/Rashi
  [3]: https://en.wikipedia.org/wiki/Pirkei_Avot
  [4]: https://en.wikipedia.org/wiki/Jacob_Emden