@article{NUMA_1976__27_132456,
     author = {O. Widlund},
     title = {On {Best} {Error} {Bounds} for {Approximation} by {Piecewise} {Polynomial} {Functions.}},
     journal = {Numerische Mathematik},
     pages = {327--338},
     publisher = {mathdoc},
     volume = {27},
     year = {1976},
     zbl = {0331.41010},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1976__27_132456/}
}