Hervé Fournier, Nutan Limaye, Guillaume Malod, Srikanth Srinivasan. Lower bounds for depth 4 formulas computing iterated matrix multiplication. In David B. Shmoys, editor, Symposium on Theory of Computing, STOC 2014, New York, NY, USA, May 31 - June 03, 2014. pages 128-135, ACM, 2014. [doi]
Abstract is missing.