An A to X of patent citations for searching

Patent citations have long been known as a useful source of information, especially in relation to trend and other analyses. This article discusses citations, but with particular emphasis on the value of citations as a regular search adjunct to conventional keyword and classification based search parameters. The different types of cited and citing references, their origins, in the jurisdictions of JP, US, EP, and WO, are described. Summaries of citation use and availability for search in the patent family databases from vendors and patent offices are provided along with example searches. Finally a section describes the value of visualisation tools, to show links between patents.