1996, James Serpell, In the Company of Animals: A Study of Human-animal Relationships, Cambridge University Press, ISBN 0521577799, p. 7The pens are equipped with ‘pig-creeps', the porcine equivalent of cat-flaps, which allow the piglets access.
2003, Pete McCarthy, McCarthy's Bar: A Journey of Discovery in Ireland, St. Martin's Press, ISBN 0312311338, p. 46,Instead, the DJ has just started a phone-in about cat-flaps.
2005, Celia Haddon, 100 Ways for a Cat to Train Its Humans, Adams Media, ISBN 1593374135, p. 42,Dine out. In urban areas there are plenty of cat-flaps allowing access to another cat's dinner.
