1. 1- Thrusfield M. Veterinary Epidemiology, 4th edition, John Wiley & Sons; 2018.
2. 2- Dohoo I, Martin W, Stryhn H. Veterinary Epidemiologic Research. 2nd ed, VER Inc; 2009.
3. 3- Malekafzali H, Majdzadeh R, Fotouhi A, Tavakoli S. Methodology of Applied Rsearches in Medical Sciences (in Persian), 1st edition, Tehran: Tehran University of Medical Sciences; 2004.
4. 4- Gordis L. Epidemiology, 6th edition, Gap; 2013.
5. 5- Mausner JS, Bahn AK. Epidemiology Principals: Iran university press; 1994.