On Generalized Indefinite Finsler Spaces John BeemM. Kishta Indiana University Mathematics Journal 1974 text pdf 10.1512/iumj.1974.23.23070 10.1512/iumj.1974.23.23070 en Indiana Univ. Math. J. 23 (1974) 845 - 853 state-of-the-art mathematics http://iumj.org/access/