- Web of Science3—index of abstracts and citations for journal articles;
- Google Scholar4—a search engine for research literature capable of examining full text of articles (not just metadata and abstracts), ranking returns by citation counts and other criteria, and providing links to related papers and accessible versions;
- Scopus5—a bibliographic data service covering all academic fields, offering citation analysis tools, owned by Elsevier;
- Web of Science6—a bibliographic data service covering all academic fields, offering citation analysis tools, owned by Thompson Reuters; and
- Microsoft Academic Search7—a relatively new, free search engine for academic papers and resources, with the capability to identify papers, authors, conferences, journals, and organizations as first class objects; display relations between these objects; and the displays of “citation in context” with snippets from citing documents.
Larger, more loosely defined data structures and services use methods of massive data analysis (NRC, 2013) for search and discovery on the vastly larger scale of the World Wide Web. These services have become essential tools for information retrieval in mathematics as in every other field. They include the following:
- Google Web Search,8
- Google Scholar10 (an index of an unknown and not easily estimated number of academic books and articles), and
- Microsoft Academic Search11 (an index of 48 million publications and more than 20 million authors across a variety of domains with updates added each week).
3 Thomson Reuters, “Web of Science Core Collection,” http://thomsonreuters.com/web-of-science/, accessed January 16, 2014.
4 Google Scholar, http://scholar.google.com/,accessed January 16, 2014.
5 Elsevier, Scopus, http://www.scopus.com/home.url, accessed January 16, 2014.
6 Thomson Reuters, “Web of Science,” http://thomsonreuters.com/products_services/science/science_products/a-z/web_of_science/, accessed January 16, 2014.
7 Microsoft Academic Search, http://academic.research.microsoft.com/,accessed January 16, 2014.
8 Google, https://www.google.com/,accessed January 16, 2014.
9 “Bing,” Wikipedia, last modified January 9, 2014, http://en.wikipedia.org/wiki/Bing.
10 Google Scholar, http://scholar.google.com/,accessed January 16, 2014.
11 “Microsoft Academic Search,” Wikipedia, last modified January 12, 2014, http://en.wikipedia.org/wiki/Microsoft_Academic_Search.