Under Art. 54(2) EPC, the state of the art comprises everything made available to the public by means of a written or oral description, by use, or in any other way, before the filing or priority date of the European patent application.

As a rule, there are no restrictions as to where, how or in what language the relevant information must have been made available to the public; nor is any limit stipulated as to how old the documents or other sources of the information may be (Guidelines G‑IV, 1 – November 2018 version).