Aghighi, M., Jonsson, P. and Ståhlberg, S. 2015. Tractable Cost-Optimal Planning over Restricted Polytree Causal Graphs. Proceedings of the AAAI Conference on Artificial Intelligence. 29, 1 (Mar. 2015). DOI:https://doi.org/10.1609/aaai.v29i1.9650.