P. Suwanbut, T. Liamsuwan, D. Nantajit, W. Masa-nga, and C. Tannanonta, “Validation of the 6 MV TrueBeam linear accelerator model for out-of-field radiation dose calculation using PHITS Monte Carlo code”, J Assoc Med Sci, vol. 54, no. 3, pp. 32–42, May 2021.