1. Bickley LS, Szilagyi PG. Bates’ guide to physical examination and history taking. 11th ed. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins; 2013.
2. Crichton N. Visual analogue scale (VAS). J Clin Nurs. 2001;10:697–706.
3. Schofield P, Aveyard B. The management of pain in older people: a workbook. 1st ed. M & K Update: Keswick; 2007.
4. McCaffery M, Beebe A. Pain: clinical manual for nursing practice. 1st ed. St. Louis: Mosby; 1989.
5. Young DM, Mentes JC, Titler MG. Acute pain management protocol. J Gerontol Nurs. 1999;25(6):10–21.