@article{AM2_1976__14_136600,
     author = {E.W. Cheney and T.A. Kilgore},
     title = {A theorem on interpolation in {Haar} subspaces.},
     journal = {Aequationes mathematicae},
     pages = {391--400},
     publisher = {mathdoc},
     volume = {14},
     year = {1976},
     zbl = {0327.41001},
     url = {http://geodesic.mathdoc.fr/item/AM2_1976__14_136600/}
}