Lane A. Hemaspaandra Kari Pasanen Jörg Rothe If P neq NP then some strongly noninvertible functions are invertible. 54-62 2006 362 Theor. Comput. Sci. 1-3 http://dx.doi.org/10.1016/j.tcs.2006.05.022 db/journals/tcs/tcs362.html#HemaspaandraPR06