@article{NUMA_1972__20_132178,
     author = {M. Golomb and R.A. Tapia},
     title = {The {Metric} {Gradient} in {Normed} {Linear} {Spaces.}},
     journal = {Numerische Mathematik},
     pages = {115--124},
     publisher = {mathdoc},
     volume = {20},
     year = {1972},
     zbl = {0277.65037},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1972__20_132178/}
}