Cal. Wat. Code § 37155.2
After the first publication of the notice required by Section 37155.1, and not less than 45 days, nor more than 60 days, before the date specified in that notice for the delivery of a collector's deed, the collector shall send by certified mail to each of the parties of interest, as specified in this section, at his or her last known address a copy of the notice published pursuant to Section 37155.1. The collector shall make a reasonable effort to ascertain the names and addresses of each of the parties of interest, including, but not limited to, the securing of a lot book guarantee from a title insurer authorized to conduct business as such in this state with respect to the delinquent property, dated as of the date of the board's demand resolution; an examination of the county's assessments of the delinquent property on the rolls beginning with the year of delinquency to and including that of the last equalized roll; an examination of the most recent telephone books in the county in which the delinquent property is located; and an examination of the telephone books covering the area of the last known address of each party of interest.
For the purposes of this section, a "party of interest" is the holder of any interest in the delinquent property which would be terminated by execution and delivery of a collector's deed.
Ca. Water Code § 37155.2