"Provide a permanent source for reference to articles of lasting interest selected from quarterly issues." Library keeps latest quarterly issues only, that are discarded when latest cumulative issue for that year is received.
Vols. 1-2 cover the period 1959-1976. Vols. 3- are annual cumulations of the quarterly with the same title. Annual vols. 3-5 (1976/77-1978/79) contain material published in the quarterly issues called vol. 18, no. 1/2-v. 20, no. 1 (1976-1978)