@article{MS2_1982__50_166786,
     author = {Erik Christensen},
     title = {Extensions of derivations {II.}},
     journal = {Mathematica Scandinavica},
     pages = {111--122},
     publisher = {mathdoc},
     volume = {50},
     year = {1982},
     zbl = {0503.47032},
     url = {http://geodesic.mathdoc.fr/item/MS2_1982__50_166786/}
}