Okayasu, Rui, Narutaka Ozawa, and Reiji Tomatsu. “Haagerup Approximation Property via Bimodules”. Mathematica Scandinavica 121, no. 1 (September 22, 2017): 75–91. Accessed July 24, 2026. https://journals.msp.org/mscand/article/view/314.