California Code, Code of Civil Procedure - CCP § 2031.210

(a) The party to whom a demand for inspection, copying, testing, or sampling has been directed shall respond separately to each item or category of item by any of the following:

(b) In the first paragraph of the response immediately below the title of the case, there shall appear the identity of the responding party, the set number, and the identity of the demanding party.

(c) Each statement of compliance, each representation, and each objection in the response shall bear the same number and be in the same sequence as the corresponding item or category in the demand, but the text of that item or category need not be repeated.

(d) If a party objects to the discovery of electronically stored information on the grounds that it is from a source that is not reasonably accessible because of undue burden or expense and that the responding party will not search the source in the absence of an agreement with the demanding party or court order, the responding party shall identify in its response the types or categories of sources of electronically stored information that it asserts are not reasonably accessible. By objecting and identifying information of a type or category of source or sources that are not reasonably accessible, the responding party preserves any objections it may have relating to that electronically stored information.