@article{EJDE_2004__2004__a130,
     author = {Nickel,  Gregor},
     title = {A new look at boundary perturbations of generators},
     journal = {Electronic journal of differential equations},
     year = {2004},
     volume = {2004},
     zbl = {1067.47053},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/EJDE_2004__2004__a130/}
}