Jun Tarui. Smallest Formulas for Parity of 2k. In Xiaodong Hu, Jie Wang, editors, Computing and Combinatorics, 14th Annual International Conference, COCOON 2008, Dalian, China, June 27-29, 2008, Proceedings. Volume 5092 of Lecture Notes in Computer Science, pages 92-99, Springer, 2008. [doi]