@article{10_4153_CMB_1990_058_0,
     author = {Pedersen, Steen},
     title = {The {Product} of two {(Unbounded)} {Derivations}},
     journal = {Canadian mathematical bulletin},
     pages = {345--348},
     year = {1990},
     volume = {33},
     number = {3},
     doi = {10.4153/CMB-1990-058-0},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1990-058-0/}
}