A Universally Hard Set of Formulae with Respect to Non-Deterministic Turing Acceptors.

Claus-Peter Schnorr H. Klupp A Universally Hard Set of Formulae with Respect to Non-Deterministic Turing Acceptors. 35-37 1977 6 Inf. Process. Lett. 2 db/journals/ipl/ipl6.html#SchnorrK77