開後圓唇元音Pennsylvania, 1997 [May 27, 2013], (原始内容存档于2005-12-23) Sailaja (2009),第24–25頁. Connolly (1990),第125頁. Tench (1990),第135頁. Dudenredaktion, Kleiner & Knöbl (2015),第38頁
拟态x. Stevens, Martin; Hopkins, Elinor; Hinde, William; Adcock, Amabel; Connolly, Yvonne; Troscianko, Tom; Cuthill, Innes C. Field Experiments on the effectiveness