@article{PORMA_1981__40_4_115465,
     author = {Olubummo, A.},
     title = {An approximation theorem for semigroups of operators},
     journal = {Portugaliae mathematica},
     pages = {383--391},
     publisher = {mathdoc},
     volume = {40},
     number = {4},
     year = {1981},
     mrnumber = {0836099},
     zbl = {0606.47041},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PORMA_1981__40_4_115465/}
}