Also of interest are books previously owned by famous persons, or personages of high stature, such as someone from royalty or the nobility. Tracing the history of an antiquarian book's possession history, referred to as "provenance", can markedly affect the value of a copy, even if it is not desirable "per se". For example, a copy of a less-important 18th-century book known to have been owned by Voltaire would achieve a value many times its stand-alone market value, simply because it was once in Voltaire's possession. Previous owners of books often signed their copies or labelled them with bookplates, and it is often not difficult to identify a prominent previous owner if the provenance is well documented. Books owned by well-known individuals that also have a connection with the author (often as a gift from the author with a written dedication to the recipient) are known as Association copies.