Chavadi Vivek Manohar, Raj Kumar Chandan, Vidushi, Khushbu Sharma, Madhuri P Lonikar, and Sukanta Sen. “A Comparative Study of Intravenous Tramadol Versus Butorphanol for Control of Shivering in Patients Undergoing Spinal Anesthesia”. Asian Pacific Journal of Health Sciences, vol. 5, no. 2, June 2018, pp. 142-7, doi:10.21276/apjhs.2018.5.2.27.