@article{MAN_1973__202_162401,
     author = {Andrew Adler and James Hamilton},
     title = {Invariant {Means} via the {Ultrapower.}},
     journal = {Mathematische Annalen},
     pages = {71--76},
     publisher = {mathdoc},
     volume = {202},
     year = {1973},
     zbl = {0235.43001},
     url = {http://geodesic.mathdoc.fr/item/MAN_1973__202_162401/}
}