Banach-valued multilinear singular integrals Francesco Di PlinioYumeng Ou Indiana University Mathematics Journal 2018 text pdf 10.1512/iumj.2018.67.7466 10.1512/iumj.2018.67.7466 en Indiana Univ. Math. J. 67 (2018) 1711 - 1763 state-of-the-art mathematics http://iumj.org/access/