There are a variety of data sources for calculating bibliometric metrics, which can be used differently depending on the provider. Although different databases often offer the same metrics, the results differ in part due to the divergent mode of operation and calculation by the providers as well as the divergent data basis. Therefore, in any bibliometric analysis, it is important to identify the data sources used.

Scopus

Scopus is a multidisciplinary database from the Elsevier company that consists largely of a curated list of journals and publications that are reviewed against quality standards before inclusion. The subject areas covered are still heavily weighted toward the natural sciences, with just under a third of the content in the social sciences.

Web of Science

Web of Science is a multidisciplinary database from the Clarivate Analytics company that is composed of several indexes. These indexes consist of a curated list of journals and publications that are screened for inclusion against quality standards. Although the focus of the disciplines covered remains on the natural sciences, Web of Science is steadily expanding its coverage to include the social sciences, arts, and humanities.

Dimensions

Dimensions is a multidisciplinary database from the Digital Science company that ingests metadata from open-access online sources and then augments the database with licensed content directly from publishers. The Dimensions platform can also be used as a bibliometric assessment tool, which distinguishes it from Web of Science and Scopus, which primarily offer bibliographic data with limited analytical tools. Dimensions offers partial free access to its system, as well as non-commercial access to its data via an API interface.

OpenAlex

OpenAlex adheres to open source principles and makes its index of data - such as scientific papers, authors and institutions - openly available. This is done through the web application via API and a full local database download snapshot for offline access.

Initiative for Open Citations (I4OC)

This initiative provides open access to scholarly citation data. The data should be machine-readable and independent of the format of the publication as well as re-usable.

Institute websites/author websites

For certain questions, websites of institutes and authors are used as a supplement.

Google Scholar

Google Scholar is a search engine for general literature research of scientific documents from Google. This includes both freely accessible documents as well as paid offers. Google Scholar analyzes and extracts the citations contained in the full texts and generates a citation analysis from them. However, the bibliometric indicators generated by Google Scholar are non-transparent in terms of content and inconsistently prepared (see an article by Mark Dingemanse on this topic).