1. Aspinall, V. & Cappello, M. (2009). Introduction to veterinary anatomy and physiology text book (2nd ed.). China: Butterworth Heinemann Elsevier. p. 166.
2. Flecknell, P. (2000). BSAVA manual of rabbit medicine and surgery. Dorset: BSAVA, pp. 41, 42, 44.