Ryszard Danecki. Nondeterministic Propositional Dynamic Logic with intersection is decidable. In Andrzej Skowron, editor, Computation Theory - Fifth Symposium, Zaborów, Poland, December 3-8, 1984, Proceedings. Volume 208 of Lecture Notes in Computer Science, pages 34-53, Springer, 1984. [doi]
Abstract is missing.