@article{10_4153_CMB_1987_045_6,
     author = {Yiu, Paul Y. H.},
     title = {Sums of {Squares} {Formulae} {With} {Integer} {Coefficients}},
     journal = {Canadian mathematical bulletin},
     pages = {318--324},
     year = {1987},
     volume = {30},
     number = {3},
     doi = {10.4153/CMB-1987-045-6},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1987-045-6/}
}