Ross, Alf, 1899- Directives and norms / by Alf Ross - London : Routledge & Kegan Paul, c1968 - ix, 188, 11 p. ; 22 cm. - International library of philosophy and scientific method . Includes index ISBN: 0710036353 : PND 4.00 Subjects--Topical Terms: Semantics (Philosophy)LogicLaw--Philosophy Dewey Class. No.: 149.9