@article{SF_1995__51_1_135422,
     author = {P. Plappert},
     title = {A sandwich theorem for monotone additive functions.},
     journal = {Semigroup forum},
     pages = {347--356},
     publisher = {mathdoc},
     volume = {51},
     number = {1},
     year = {1995},
     zbl = {0834.20060},
     url = {http://geodesic.mathdoc.fr/item/SF_1995__51_1_135422/}
}