Li, Fengling, Fengchun Lei, and Guoqiu Yang. “Some Sufficient Conditions for Heegaard Genera to Be Additive Under Annulus Sum”. MATHEMATICA SCANDINAVICA 115, no. 2 (December 3, 2014): 173–188. Accessed August 14, 2026. https://tidsskrift.dk/math/article/view/19221.