Using the introductory signal "cf," Justice Traynor cites to James Baird Co. v. Gimbel Bros, 64 F.2d 344 (2d Cir. 1933), an opinion written by another eminent jurist of the 20th century, Judge Learned Hand.  The signal "cf" is intended to convey that the cited authority supports a proposition different from the main proposition but sufficiently analagous to lend support.  See The Bluebook, A Uniform System of Citation 23 (16th Ed. Harvard Law Review Association).  Traynor was a scholar and academic prior to his appointment to the California Supreme Court and was presumably familiar with the use of signals ("cf" meant the same thing in 1958 when he wrote the Drennan opinion as it does now).  After reading Drennan, read (or reread) the Gimbel Bros. opinion and decide whether you think that the signal "cf" is appropriate.