@article{NUMA_1983__42_132864,
     author = {Florencio Utreras},
     title = {Natural {Spline} {Functions,} {Their} {Associated} {Eigenvalue} {Problem.}},
     journal = {Numerische Mathematik},
     pages = {107--118},
     publisher = {mathdoc},
     volume = {42},
     year = {1983},
     zbl = {0522.41011},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1983__42_132864/}
}