I belong (belonged) to the

• American Mathematical Society , from 1976 on
• Romanian Mathematical Society, from 1976 to 1990
• European Association for Theoretical Computer Science, from 1983 on (Member of the Council, 1995-2003)
• New Zealand Computer Science Society, from 1993 to 1995
• New Zealand Mathematical Society, from 1993 on
• European Association for Computer Science Logic, from 1994 to 1996
• New York Academy of Sciences, from 1994 to 1996
• International Scientific Council Black Sea University, Bucharest, Romania, from 1994 to 2000
• The Kurt Goedel Society , Vienna, Austria, from 1996 on
• New Zealand Royal Society, from 1997 to 2012
• Academia Europaea, from 2008 on