Some Bi-Matrix Models for Bi-Free Limit Distributions Paul Skoufranis Indiana University Mathematics Journal 2017 text pdf 10.1512/iumj.2017.66.6114 10.1512/iumj.2017.66.6114 en Indiana Univ. Math. J. 66 (2017) 1755 - 1795 state-of-the-art mathematics http://iumj.org/access/