@article{10_4064_ap_22_2_229_237,
     author = {M. Kuczma},
     title = {On squares of differentiable functions},
     journal = {Annales Polonici Mathematici},
     pages = {229--237},
     publisher = {mathdoc},
     volume = {22},
     number = {2},
     year = {1969},
     doi = {10.4064/ap-22-2-229-237},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/ap-22-2-229-237/}
}