Hoseininia, S., S. M.-. Kebar, and K. G.-. Kheir. “Study the Frequency of Bronchial Anthracosis and Its Influencing Factors in Patients Undergoing Bronchoscopy in Ardabil City Hospital, 2013-2015”. International Journal Of Community Medicine And Public Health, vol. 7, no. 10, Sept. 2020, pp. 3843-6, doi:10.18203/2394-6040.ijcmph20204348.