@article{10_1017_S0017089500008612,
     author = {Takaguchi, Makoto},
     title = {Centers of mass for operator-families},
     journal = {Glasgow mathematical journal},
     pages = {123--126},
     year = {1992},
     volume = {34},
     number = {1},
     doi = {10.1017/S0017089500008612},
     url = {http://geodesic.mathdoc.fr/articles/10.1017/S0017089500008612/}
}