@article{10_4153_CMB_2003_041_9,
     author = {Marshall, M.},
     title = {Approximating {Positive} {Polynomials} {Using} {Sums} of {Squares}},
     journal = {Canadian mathematical bulletin},
     pages = {400--418},
     year = {2003},
     volume = {46},
     number = {3},
     doi = {10.4153/CMB-2003-041-9},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-2003-041-9/}
}