Morris, V., Salem, M., Nimeiri, H., Iqbal, S., Singh, P., Ciombor, K., … Eng, C. (2017). Nivolumab for previously treated unresectable metastatic anal cancer (NCI9673): a multicentre, single-arm, phase 2 study. The Lancet. Oncology, 18(4), 446-453. https://doi.org/10.1016/S1470-2045(17)30104-3