@article{10_4153_CJM_1968_111_0,
     author = {Goodman, A. W.},
     title = {The {Valence} of {Sums} and {Products}},
     journal = {Canadian journal of mathematics},
     pages = {1173--1177},
     year = {1968},
     volume = {20},
     number = {1},
     doi = {10.4153/CJM-1968-111-0},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1968-111-0/}
}