Azwan, N. A. B., R. K. S. Shanmugam, and K. Y. Teng. “A Nearly Missed Foreign Body in Frontal Sinus: Case Report”. International Journal of Otorhinolaryngology and Head and Neck Surgery, vol. 6, no. 2, Jan. 2020, pp. 425-7, doi:10.18203/issn.2454-5929.ijohns20200164.