@article{PORMA_1951__10_1_114493,
     author = {Protter, M.H.},
     title = {On a class of harmonic polynomials},
     journal = {Portugaliae mathematica},
     pages = {11--22},
     publisher = {mathdoc},
     volume = {10},
     number = {1},
     year = {1951},
     mrnumber = {0041993},
     zbl = {0043.07302},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PORMA_1951__10_1_114493/}
}