Spinor Space and Line Geometry II Vaiclav Hlavaty Indiana University Mathematics Journal 1952 text pdf 10.1512/iumj.1952.1.51008 10.1512/iumj.1952.1.51008 en Indiana Univ. Math. J. 1 (1952) 321 - 339 state-of-the-art mathematics http://iumj.org/access/