@article{MET_1987__34_176094,
     author = {M.C. Spruill},
     title = {Optimal {Extrapolation} of {Derivatives.}},
     journal = {Metrika},
     pages = {45--60},
     publisher = {mathdoc},
     volume = {34},
     year = {1987},
     zbl = {0608.62088},
     url = {http://geodesic.mathdoc.fr/item/MET_1987__34_176094/}
}