He was instrumental in the development of the historic agreement between the Reformed and Eastern Orthodox churches on the doctrine of the Trinity when a joint statement of agreement on that doctrine was issued between the World Alliance of Reformed Churches and the Orthodox Church on 13 March 1991.
Ia merupakan tokoh penting dalam pengembangan perjanjian bersejarah antara Gereja Reformed dan Ortodoks Timur tentang doktrin Tritunggal saat sebuah pernyataan bersama tentang perjanjian doktrin tersebut dikeluarkan antara Aliansi Gereja-gereja Reformed Dunia dan Gereja Ortodoks pada 13 Maret 1991.