Jonas, Marty (1998-02-11). "Eisenstein". International Committee of the Fourth International (ICFI). Archived from the original on 2008-02-22. Retrieved 2010-04-25.
Jonas, Marty (1998-02-11). "Eisenstein". International Committee of the Fourth International (ICFI). Archived from the original on 2008-02-22. Retrieved 2010-04-25.