Citation index in the context of Science Citation Index Expanded

The Social Sciences Citation Index (SSCI) is a commercial citation index product of Clarivate Analytics. It was originally developed by the Institute for Scientific Information from the Science Citation Index. The Social Sciences Citation Index is a multidisciplinary index which indexes over 3,400 journals across 58 social science disciplines – 1985 to present, and it has 122 million cited references – 1900 to present.

It also includes a range of 3,500 selected items from some of the world's finest scientific and technical journals. It has a range of useful search functions such as 'cited reference searching', searching by author, subject, or title.

The Arts and Humanities Citation Index (AHCI), also known as Arts and Humanities Search, is a citation index, with abstracting and indexing for more than 1,700 arts and humanities academic journals. Part of this database is derived from Current Contents.

Subjects covered are the arts, humanities, language (including linguistics), poetry, music, classical works, history, oriental studies, philosophy, archaeology, architecture, religion, television, theater, and radio.

The Emerging Sources Citation Index (ESCI) is a citation index produced since 2015 by Thomson Reuters and now by Clarivate. According to the publisher, the index includes "peer-reviewed publications of regional importance and in emerging scientific fields".

The ESCI is accessible through the Web of Science, together with other Clarivate indexes. As of June 2021, all journals indexed in ESCI are also included in the Journal Citation Reports. While these journals still did not receive an impact factor until the next year, they did contribute citations to the calculation of other journals' impact factors. In July 2022, Clarivate announced that journals in the ESCI obtain an impact factor effective from JCR Year 2022 first released in June 2023.