@article{MAN_1975__216_162724,
     author = {W.H. Schikhof},
     title = {The {Set} of {Derivatives} in a {Non-Archimedean} {Field.}},
     journal = {Mathematische Annalen},
     pages = {67--70},
     publisher = {mathdoc},
     volume = {216},
     year = {1975},
     zbl = {0308.12102},
     url = {http://geodesic.mathdoc.fr/item/MAN_1975__216_162724/}
}