Delivering a core list of key headings, together with patterns and examples to guide the cataloger in creating further headings as required, Sears List of Subject Headings has been the standard thesaurus of subject terminology for small and medium-sized libraries since 1923. This essential resource features: Agreement with the Dewey Decimal Classification system to ensure that subject headings conform with library standards. Easy-to-use thesaurus-like format. Accompanying list of canceled and replacement headings, and legends within the list that identify earlier forms of headings. The 20th edition of the Sears List features expanded coverage for developing topics, as well as updated headings in some areas. New headings in this edition reflect the growing literature in areas such as ecology and the environment, including: Rainforest ecology Grassland ecology Climate change Sustainable agriculture Headings have also been established for the different types of dinosaur, including: Raptorex Pteranodon Edmontosaurus New trends in social networking are represented by entries like Twitter and Facebook. And new headings for arts and crafts have also been added, such as Acrylic painting and Wire craft. Soviet Union headings have been canceled in favor of period subdivision under Russia—History. Indians has been re-established to denote the people of India. A number of headings for the literature and culture of India—such as Indian music and Indian literature—have been reconciled with this change, and new chronological subdivisions have been established for the history of India. Sears List of Subject Headings also includes "Principles of the Sears List", a 23-page insert outlining the theoretical foundations of the Sears List and the general principles of subject cataloging.