Tanaka, Hidekazu, Takahiro Yamaguchi, Kae Hachiya, Masashi Kitahara, Katsuya Matsuyama, Sunaho Okada, and Masayuki Matsuo. “The Field-in-Field Technique in Esophageal Cancer Radiotherapy”. European Journal of Oncology and Environmental Health 22, no. 2 (November 17, 2017): 71–75. Accessed January 24, 2022. https://www.mattioli1885journals.com/index.php/EJOEH/article/view/6200.