@article{10_4064_cm_28_2_275_285,
     author = {N. K. Kundu},
     title = {On approximate symmetric derivative},
     journal = {Colloquium Mathematicum},
     pages = {275--285},
     publisher = {mathdoc},
     volume = {28},
     number = {2},
     year = {1973},
     doi = {10.4064/cm-28-2-275-285},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/cm-28-2-275-285/}
}