@article{10_4064_ap_23_3_247_253,
     author = {N. K. Kundu and S. N. Mukhopadhyay},
     title = {Symmetric derivative of nowhere monotone functions, {I}},
     journal = {Annales Polonici Mathematici},
     pages = {247--253},
     publisher = {mathdoc},
     volume = {23},
     number = {3},
     year = {1970},
     doi = {10.4064/ap-23-3-247-253},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/ap-23-3-247-253/}
}