to select Member Nations and Associate Members inviting them to appoint members of this Committee on the basis of their technical competence, such selection by the Director-General of Member Nations and Associate Members being effected in the light of the desirability that the Committee membership should be not less than twelve and not more than twenty, and that its composition should be representative of the different regions of the world and of countries with long-established institutions for training forestry personnel at the professional and technical levels;