@article{MS2_1967__21_166020,
     author = {M.A. Perles and G.C. Shepard},
     title = {Angle {Sums} of {Convex} {Polytopes.}},
     journal = {Mathematica Scandinavica},
     pages = {199--218},
     publisher = {mathdoc},
     volume = {21},
     year = {1967},
     zbl = {0172.23703},
     url = {http://geodesic.mathdoc.fr/item/MS2_1967__21_166020/}
}