 | B. Mashhon , University of Missouri-Columbia, Columbia, USA, Sep. 1 - Oct. 1, 1991 |
 | H. Woodin , University of California, Berkeley, Berkeley, USA, Aug. 1 - Sep. 1, 1991 |
 | K. Hauser , University of California, Berkeley, Berkeley, USA, Aug. 1 - Sep. 1, 1991 |
 | J. Larson , University of Florida, Gainesville, USA, Aug. 1 - Sep. 1, 1991 |
 | R. Laver , University of Colorado, Boulder, USA, Aug. 1 - Sep. 1, 1991 |
 | W. Mitchell , University of Florida, Gainesville, USA, Aug. 1 - Sep. 1, 1991 |
 | M.A. Shokrollahi , Informatics Institute, Bonn, Germany, Dec. 1, 1990 - Jan. 1, 1991 |
 | S. Shokranian , University of Brasilia, Brasilia, Brazil, Dec. 1, 1990 - Jan. 1, 1991 |
 | A.H. Assadi , University of Wisconsin-Madison, Wisconsin, USA, March 1, 1990 - June 1, 1991 |
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