@article{tplp/HeyninckB23, 
    title={Non-deterministic Approximation Operators: Ultimate Operators, Semi-equilibrium Semantics, and Aggregates}, 
    volume={23}, 
    DOI={10.1017/S1471068423000236}, 
    number={4}, 
    journal={Theory and Practice of Logic Programming}, 
    author={HEYNINCK, JESSE and BOGAERTS, BART}, 
    year={2023}, 
    pages={632--647}}