The paper On the Axiomatisation of Branching Bisimulation Congruence over CCS by Luca Aceto, Valentina Castiglioni, Anna Ingólfsdóttir and Bas Luttik was presented at CONCUR 2022 on September 13, 2022. In the paper, which is available here, it is proved that CCS proper is not finitely based modulo rooted branching bisimilarity, but that a finite basis exists if left merge and communication merge are added.
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