@article{10_14708_cm_v25i1_6109,
     author = {Z. Bogucki and J. Zderkiewicz},
     title = {Sur la courbure des lignes de niveau et de leurs trajectoires orthogonales dans la classe \(\sum_{\alpha k}^c\) des fonctions sigme convexex d{\textquoteright}ordre \(\alpha\) et k-sym\'etriques},
     journal = {Commentationes Mathematicae},
     pages = { 1--4},
     publisher = {mathdoc},
     volume = {25},
     number = {1},
     year = {1985},
     doi = {10.14708/cm.v25i1.6109},
     language = {pl},
     url = {http://geodesic.mathdoc.fr/articles/10.14708/cm.v25i1.6109/}
}