California Code, Government Code - GOV § 66499.57

Whenever the city council or board of supervisors adopts a map prepared under this division as the official map of the subdivision, town, city or county, it shall be lawful and sufficient to describe the lots or blocks in any deeds, conveyances, contracts, or obligations affecting any of the lots or blocks as designated on the official map, a reference sufficient for the identification of the map being coupled with the description.