The Convention on the Grant of European Patents of 5 October 1973, commonly known as the European Patent Convention (EPC), is a multilateral treaty instituting the European Patent Organisation and providing an autonomous legal system according to which European patents are granted. The term European patent is used to refer to patents granted under the European Patent Convention. The granting of the patent is subject to central revocation or narrowing as a group pursuant to two types of unified, post-grant procedures: a time-limited opposition procedure, which can be initiated by any person except the patent proprietor, and limitation and revocation procedures, which can be initiated by the patent proprietor only.