@article{10_4153_CMB_1972_073_9,
     author = {Stewart, James},
     title = {Functions with a {Finite} {Number} of {Negative} {Squares}},
     journal = {Canadian mathematical bulletin},
     pages = {399--410},
     year = {1972},
     volume = {15},
     number = {3},
     doi = {10.4153/CMB-1972-073-9},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1972-073-9/}
}