During the 1970s and 80s, he was also a Visiting Professor at the California Institute of Technology, the University of Wisconsin–Milwaukee and the University of California, Berkeley.
В течение 1970-х и 1980-х годов он читал лекции в Калифорнийском технологическом институте, в университете Висконсин-Милуоки и Калифорнийском университете в Беркли.