(en) DISTRICT OF COLUMBIA APPROPRIATION BILL FOR 1939 HEARINGS BEFORE THE SUBCOMMITTEE OF THE COMMITTEE ON APPROPRIATIONS UNITED STATES SENATE, (lire en ligne)
(en) Negligence and Compensation Cases Annotated, Callaghan, (lire en ligne)
In (en) Brevet U.S. 1471465 Hinton wrote on page 3, "Again and importantly, the monkey instinct strong in all human beings and perhaps more clearly displayed in children, makes climbing a sport to which children enthusiastically take, by a psychology about the same as that of a kitten at play with a ball, which of course is practice for hunting."
