Datalog with Non-Deterministic Choice Computes NDB-PTIME. - Luca Corciulo; Fosca Giannotti; Dino Pedreschi (DOOD, 1993)

Expressive Power of Non-Deterministic Operators for Logic-based Languages. - Luca Corciulo; Fosca Giannotti; Dino Pedreschi; Carlo Zaniolo (Workshop on Deductive Databases and Logic Programming, 1994)