Dai, X., C. Fu, C. Wang, Y. Cai, S. Zhang, W. Guo, and D. Kuang. “ The Impact of Tracheotomy on Levels of Procalcitonin in Patients Without Sepsis: A Prospective Study ”. Clinics, vol. 70, no. 9, Sept. 2015, pp. 612-7, doi:10.6061/clinics/2015(09)03.