He was an invited speaker at the International Congress of Mathematicians in 1974 at Vancouver and in 1986 at Berkeley, and a plenary speaker at the ICM in 1978 at Helsinki.
hiː wʌz ɐn ɪnvˈaɪɾᵻd spˈiːkɚɹ æt ðɪ ˌɪntɚnˈæʃənəl kˈɑːŋɡɹəs ʌv mˌæθɪmɐtˈɪʃənz ɪn nˈaɪntiːnhˈʌndɹɪd sˈɛvənti fˈoːɹ æt væŋkˈuːvɚ ænd ɪn nˈaɪntiːnhˈʌndɹɪd ˈeɪɾi sˈɪks æt bˈɜːkli, ænd ɐ plˈiːnɚɹi spˈiːkɚɹ æt ðɪ ˌaɪsˌiːˈɛm ɪn nˈaɪntiːnhˈʌndɹɪd sˈɛvənti ˈeɪt æt hɛlsˈɪŋki.