Cal. Sts. & Hy. Code § 3113
The legislative body shall not order a modification in the boundaries of a district shown on a previously filed map of the district unless the legislative body describes the proposed modification by reference to an amended map of the district boundary. The amended map shall be approved by resolution adopted by the legislative body and the clerk of the legislative body shall file the amended map showing the modification of boundaries of the district with the county recorder not later than 15 days after the resolution of the legislative body approving the amended boundary. The map shall also contain the legends provided for in Section 3110.
The county recorder shall endorse the time and date of the filing upon the modified or amended boundary map that is stored in the recorder's office pursuant to Section 3112. The county recorder shall cross-index the amended boundary map by reference to page and book of maps of assessment and community facilities districts in which the original boundary map of the affected district was filed.
The amended boundary map shall include on its face that it amends the boundary map for (here insert name or number of district or both name and number of district, together with city or county, or both city and county), State of California, prior recorded at Book __ of Maps of Assessment and Community Facilities Districts at page __, in the office of the County Recorder for the County of ____, State of California.
Ca. Sts. and High. Code § 3113