On non-linear lower bounds in computational complexity. Leslie G. Valiant. Dana Angluin and Leslie G. Valiant. Fast probabilistic algorithms for Hamiltonian circuits and matchings. L. G. Valiant.
Negation can be exponentially powerful.
L. G. Valiant. Completeness classes in algebra. L. G. Valiant and G. J. Brebner. Universal schemes for parallel communication. John H. Reif and Leslie G. Valiant.