The fourth session of the Working Group was held at Unesco headquarters in May. Participating members were: S.K. Banerjee (India); S. Cavassa (Italy); H. Kikkawa (Japan); W. Meyer (Poland); F.F. Snyder (U.S.);; Chairman A.A. Sokolov (USSR); and V. Stanescu (Romania). M. Podani represented the World Meteorological Organization (WMO) at the meeting.