Cal. RTC § 6362.7

(a) There are exempted from the taxes imposed by this part, the gross receipts from the sale of, and the storage, use, or other consumption in this state, of tangible personal property which becomes an ingredient or component part of any newspaper or periodical that is distributed without charge and regularly issued at average intervals not exceeding three months, and any such newspaper or periodical.

(b) There are exempted from the taxes imposed by this part, the gross receipts from the sale of, and the storage, use, or other consumption in this state, of tangible personal property which becomes an ingredient or a component part of any periodical regularly issued at average intervals not exceeding three months, and any such periodical, that is sold by subscription and delivered by mail or common carrier.

(c) For purposes of this section, “periodical” means any publication that appears at stated intervals at least four times per year, but not more than 60 times per year, each issue of which contains news or information of general interest to the public, or to some particular organization or group of persons. Each issue must bear a relationship to prior or subsequent issues with respect to continuity of literary character or similarity of subject matter, and there must be some connection between the different issues of the series in the nature of the articles appearing in them. Each issue must be sufficiently similar in style and format to make it evident that it is one of a series. The term does not include printed sales messages, shopping guides, or other publications of which the advertising portion, including product publicity, exceeds 90 percent of the printed area of the entire issue in more than one-half of the issues during any 12-month period.