@article{NUMA_1975__25_132375,
     author = {R.E. Barnhill and J.A. Gregory},
     title = {Sard {Kernel} {Theorems} on {Triangular} {Domains} with {Application} to {Finite} {Element} {Error} {Bounds.}},
     journal = {Numerische Mathematik},
     pages = {215--230},
     publisher = {mathdoc},
     volume = {25},
     year = {1975},
     zbl = {0304.65076},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1975__25_132375/}
}