Each issue has also distinctive title; Excerpta medica; Biological abstracts; Chemical abstracts; Energy research abstracts; Index medicus; Life sciences collection; International nursing index; Nuclear science abstracts; Issues for June 1943-Dec. 1958 have no vol. numbering but constitute v. 23, no. 3-v. 38, no. 6; Beginning with 1940, the Dec. issue includes a three year cumulative index