California Code, Streets and Highways Code - SHC § 10354

If said resolution proposes to include additional territory in the assessment district, or to increase any assessment, at least 20 days prior to the hearing fixed therein the clerk of the legislative body shall mail a copy of said resolution to all persons owning real property within said additional territory, or whose assessment is increased, whose names and addresses appear on the last equalized assessment roll or as known to said clerk.