Economic regionalization : materials of the First General Meeting of the Commission held in Utrecht, the Netherlands, from 8 till 9. Sept. 1961 = Regionalizacja ekonomiczna : materiały z I Zebrania Ogólnego Komisji w Utrechcie, Holandia, w dniach 8-9. IX 1961 - General Meeting of the Commission on Methods of Economic Regionalization International Geographical Union (1 ; 1961 ; Utrecht) (1962)