@article{MZ_1993__212_4_174509,
     author = {R. de Laubenfels},
     title = {Matrices of operators and regularized semigroups.},
     journal = {Mathematische Zeitschrift},
     pages = {619--630},
     publisher = {mathdoc},
     volume = {212},
     number = {4},
     year = {1993},
     zbl = {0792.47041},
     url = {http://geodesic.mathdoc.fr/item/MZ_1993__212_4_174509/}
}