(EN) AKC Staff Jan 01, 2009, Why Are German Shepherds So Popular?, su American Kennel Club. URL consultato il 28 maggio 2021.
«1921. Strongheart makes his screen debut. A police dog turned actor, Strongheart becomes the first dog to become a genuine movie star. His success opens the door for an even bigger star, Rin Tin Tin. Their movies endear the breed to audiences around the world.»
