@article{MAN_1981__258_163592,
     author = {Frank Hansen and Gerd Kjaergard Pedersen},
     title = {Jensen's {Inequality} for {Operators} and {L\"owner} 's {Theorem.}},
     journal = {Mathematische Annalen},
     pages = {229--242},
     publisher = {mathdoc},
     volume = {258},
     year = {1981},
     zbl = {0473.47011},
     url = {http://geodesic.mathdoc.fr/item/MAN_1981__258_163592/}
}