Since 1993 he has been a professor at Tulane University .
For the academic year 1991 -- 1992 he was a visiting professor at the University of Maryland and for the academic year 1992 -- 93 at the University of Minnesota .
Since 1993 visiting professor has been a visiting professor at Tulane University .
For the academic year 1991 -- 1992 he was a visiting professor at the University of Maryland and for the academic year 1992 -- 93 at the University of Minnesota .