@article{AULFM_1987_02_a5,
     author = {L\k{e}dzewicz-Kowalewska, Urszula},
     title = {The extremum principle for problems of optimal control with mixed constraints},
     journal = {Acta Universitatis Lodziensis. Folia Mathematica},
     publisher = {mathdoc},
     volume = {02},
     year = {1987},
     language = {pl},
     url = {http://geodesic.mathdoc.fr/item/AULFM_1987_02_a5/}
}