Trivializations of Orthogonal Bundles Mingxue Liu Indiana University Mathematics Journal 1973 text pdf 10.1512/iumj.1973.22.22019 10.1512/iumj.1973.22.22019 en Indiana Univ. Math. J. 22 (1973) 227 - 231 state-of-the-art mathematics http://iumj.org/access/