1. Haynes RB, Sackett DL, Guyatt GH, Tugwell P. Clinical epidemiology: how to do clinical practice research. 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2006.
2. Sackett D, Richardson WS, Rosenburg W, Haynes RB. How to practice and teach evidence based medicine. 2nd ed. London, England: Churchill Livingstone; 1997.
3. Thoma A, McKnight L, McKay P, Haines T. Forming the research question. Clin Plast Surg. 2008;35(2):189–93.
4. Hulley SB, Cummings SR, Browners WS, Grady DG, Newman TB. Conceiving the research question and developing the study plan. In: Gaertner R, editor. Designing clinical research. 4th ed. Philadelphia, PA: Lippincott Williams & Wilkins, a Wolters Kluwer business; 2013. p. 14–22.
5. Thabane L, Thomas T, Ye C, Paul J. Posing the research question: not so simple. Can J Anesth. 2009;56:71–9.