[1]
Thuần, H. and Giao, H.T.L. 2012. Discuss with properties a P.F. should posses and what constitutes a resonable extension of an operator relative to a given P. E. Journal of Computer Science and Cybernetics. 19, 4 (Jul. 2012), 359–365. DOI:https://doi.org/10.15625/1813-9663/19/4/1544.