Evaluation of analgesic and physiologic effects of epidural morphine administered at a thoracic or lumbar level in dogs undergoing thoracotomy - Carregaro, Adriano Bonfim; Freitas, Gabrielle Coelho; Lopes, Carlize; Lukarsewski, Rafael; Tamiozzo, Fernanda Siqueira; Santos, Rogério Rodrigues (Veterinary Anaesthesia and Analgesia, 2014)