Involutions Fixing the Disjoint Union of Two Projective Spaces David Royster Indiana University Mathematics Journal 1980 text pdf 10.1512/iumj.1980.29.29018 10.1512/iumj.1980.29.29018 en Indiana Univ. Math. J. 29 (1980) 267 - 276 state-of-the-art mathematics http://iumj.org/access/