The set is arranged alphabetically by scientist. The index allows one to search by topic of science and find entries about the scientists who made contributions in that area. Notable Twentieth-Century Scientists. Gale Research Inc., c. 1995. This four volume set provides biographies for 1,300 scientists who lived during the twentieth century.
Indexes allow searching by nationality, gender, specialization and subject.
A Biographical Dictionary. By Martha J. Bailey. ABC-CLIO, c. 1994. One volume book focusing on American women scientists primarily in the physical and natural sciences in the nineteenth and early twentieth centuries. Entries are brief, but provide good background information.