The Integral Cohomology Rings of the Classifying Spaces of O(n) and SO(n) Mark Feshbach Indiana University Mathematics Journal 1983 text pdf 10.1512/iumj.1983.32.32036 10.1512/iumj.1983.32.32036 en Indiana Univ. Math. J. 32 (1983) 511 - 516 state-of-the-art mathematics http://iumj.org/access/