A substantial fraction of all technical literature deals with some type of information about materials. The Directory of Information Resources in the United States (Library of Congress) identified 2891 sources of information in 1974, other than publications, in the physical sciences and engineeing. A large fraction of these also dealt with some aspect of information about materials

The general card catalogs, lists of publications, and abstracts that cover the published literature are presumably known to readers of this Handbook and will not be discussed here. However, this should not be taken as a suggestion that a traditional literature search can safely be omitted when seeking information about an unfamiliar material. Some knowledge of the material is essential both to pose a question that will elicit a useful response and to judge which source is likely to contain the information needed.