Chistikov, D., G. Lisowski, M. Paterson, and P. Turrini. “Convergence of Opinion Diffusion Is PSPACE-Complete”. Proceedings of the AAAI Conference on Artificial Intelligence, vol. 34, no. 05, Apr. 2020, pp. 7103-10, doi:10.1609/aaai.v34i05.6197.