@article{MAN_1969__181_161839,
     author = {F.S. KOEHL},
     title = {Difference {Properties} for {Banach-Valued} {Functions.}},
     journal = {Mathematische Annalen},
     pages = {288--296},
     year = {1969},
     volume = {181},
     zbl = {0164.15901},
     url = {http://geodesic.mathdoc.fr/item/MAN_1969__181_161839/}
}