Aziz, H., E. Elkind, S. Huang, M. Lackner, L. Sanchez-Fernandez, and P. Skowron. “On the Complexity of Extended and Proportional Justified Representation”. Proceedings of the AAAI Conference on Artificial Intelligence, vol. 32, no. 1, Apr. 2018, https://ojs.aaai.org/index.php/AAAI/article/view/11478.