@article{AM2_1981__22_136872,
     author = {L. Flatto and D. Jacobson},
     title = {Functions satisfying a discrete mean value property.},
     journal = {Aequationes mathematicae},
     pages = {173--193},
     publisher = {mathdoc},
     volume = {22},
     year = {1981},
     zbl = {0486.31005},
     url = {http://geodesic.mathdoc.fr/item/AM2_1981__22_136872/}
}