@article{10_4153_CMB_2011_128_6,
     author = {Ayuso, P. Fortuny},
     title = {Derivations and {Valuation} {Rings}},
     journal = {Canadian mathematical bulletin},
     pages = {31--38},
     year = {2013},
     volume = {56},
     number = {1},
     doi = {10.4153/CMB-2011-128-6},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-2011-128-6/}
}