What is the test for determining whether a party can be found liable for trademark infringement?

The district court's primary task, in determining infringement of registered trademarks, is to make the factual determination whether the public is likely to be deceived or confused by the similarity of the marks as to source, relationship or sponsorship. See Smith v. Chanel, Inc., 402 F.2d 562, 563 (9th Cir.1968). Regardless of what specific factors are discussed by the district court, we review the district court's ultimate factual finding under the clearly erroneous standard.