1st

New York, NY

16 April 1960

2nd

New York, NY

16 December 1961

3rd

Washington, DC

20 April 1962

4th

Toronto, Ont.

  7 September 1963

5th

New York, NY

11 September 1964

6th

Chicago, IL

18 September 1965

7th

New York, NY

  2 September 1966

8th

Montreal, P.Q.

  1 July 1967

9th

Washington, DC

30 August 1968

10th

New York, NY

  4 October 1969

11th

New York, NY

13 November 1970

12th

New York, NY

  6 November 1971

13th

Washington, DC

10 November 1972

14th

Toronto, Ont.

17 November 1973

15th

New York, NY

15 November 1974

16th

Los Angeles, CA

24 October 1975

17th

Washington, DC

12 August 1976

18th

Ottawa, Ont.

7 October 1977

19th

Cleveland, OH

26 October 1978

20th

Los Angeles, CA

26 October 1979

21st

Washington, DC

17 October 1980

22nd

Montreal, P.Q.

23 October 1981

23rd

Pittsburgh, PA

29 October 1982

24th

Cambridge, MA

4 November 1983

25th

Toronto, Ont.

25 October 1984

26th

Thun, Switzereland

11 August 1985

27th

Boston, MA

18 September 1986

28th

Los Angles, CA

18 September 1987

29th

Washington, DC

15 September 1988

30th

Bethlehem, PA

13 October 1989

31st

Toronto, Ont.

11 October 1990

32nd

Chicago, IL

21 September 1991

33rd

24 October 1992

34th

Washington, DC

11 December 1993

35th

New York, NY

29 October 1994

36th

Kosice, SR

21 August, 1995

37th

Brno, CR

28 August 1996

38th

Elton, TX

12 July 1997

39th

Bratislava, SR

  7 July 1998

40th

24 April 1999

41st

Washington, DC

10 August 2000