@article{10_4064_ap_8_1_1_4,
     author = {Stanis{\l}aw Go{\l}\k{a}b},
     title = {On the notion of gradient. {I.} {Essentiality} of regularity suppositions},
     journal = {Annales Polonici Mathematici},
     pages = {1--4},
     publisher = {mathdoc},
     volume = {8},
     number = {1},
     year = {1960},
     doi = {10.4064/ap-8-1-1-4},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/ap-8-1-1-4/}
}