^Parker, Mark S.; Chasen, Marvin H.; Paul, Narinder (1 March 2009). "Radiologic Signs in Thoracic Imaging: Case-Based Review and Self-Assessment Module". American Journal of Roentgenology. 192 (3_supplement): S34–S48. doi:10.2214/AJR.07.7081. ISSN 0361-803X. Retrieved 23 April 2019.