@article{MAN_1981__256_163494,
     author = {Frank Hansen},
     title = {Selfadjoint {Means} and {Operator} {Monotone} {Functions.}},
     journal = {Mathematische Annalen},
     pages = {29--36},
     publisher = {mathdoc},
     volume = {256},
     year = {1981},
     zbl = {0461.47009},
     url = {http://geodesic.mathdoc.fr/item/MAN_1981__256_163494/}
}