@article{MZ_1991__208_3_174337,
     author = {Vu Quoc Ph\'ong},
     title = {The operator equation {AX} - {XB} = {C} with unbounded operators {A} and {B} and related abstract {Cauchy} problems.},
     journal = {Mathematische Zeitschrift},
     pages = {567--588},
     publisher = {mathdoc},
     volume = {208},
     number = {3},
     year = {1991},
     zbl = {0726.47029},
     url = {http://geodesic.mathdoc.fr/item/MZ_1991__208_3_174337/}
}