@article{IM_1977__43_142505,
     author = {Erik Christensen},
     title = {Perturbation of {Operator} {Algebras.}},
     journal = {Inventiones mathematicae},
     pages = {1--14},
     publisher = {mathdoc},
     volume = {43},
     year = {1977},
     zbl = {0366.46050},
     url = {http://geodesic.mathdoc.fr/item/IM_1977__43_142505/}
}