Cal. Health and Safety Code § 4610.5

Copies of the resolution shall also be posted in three public places within the proposed district not earlier than the 60th day or later than the 30th day prior to the hearing. Not earlier than 60 nor later than 30 days prior to the hearing, a copy of the resolution shall also be mailed, postage prepaid, to each person to whom land in the proposed district is assessed as such owner is shown on the last equalized county assessment roll, at his address as shown upon the roll, and to each person who has any interest in any land within the proposed district whose name and address and a designation of the land in which he is interested is on file in the office of the city clerk. Any error, omission, or mistake in such mailing, or any failure of any person to receive such copy shall not invalidate the proceedings pursuant to this chapter.