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He completed post-doctoral studies at the University of Nijmegen in the Netherlands, and later served as visiting fellow and professor in Trieste, Camerino, Perugia, and Rome, all in Italy, Uppsala in Sweden, Brno in the Czech Republic, Perth in Australia and Pretoria and Stellenbosch, both in South Africa.
In 1966 he became a Fulbright professor at the University of Nijmegen, the Netherlands.