Kari Rantanen received the PGM 2018 Best Student Paper Award for the paper Learning Optimal Causal Graphs with Exact Search, co-authored with Antti Hyttinen and Matti Järvisalo, and with Kari as the first author. The paper presents the first truly specialized exact search algorithm for optimal causal graphs in a general model space, allowing both cycles and latent confounding variables, and combining problem-specific branch-and-bound style search with linear programming based bounding. The resulting system bcause constitutes empirically a new state-of-the-art approach to the problem.