[MathOuvrage]
Positive polynomials and sums of squares
/ Marshall, Murray A..
-Providence RI : American mathematical Society, 2008. - xii, 187 p. ; 26 cm
ISBN 9780821844021
[MathOuvrage]
A Guide to elementary number theory
/ Dudley, Underwood.
-Washington DC : Mathematical Association of America, 2010. - x, 139 p. ; 23 cm
ISBN 9780883853474
[MathOuvrage]
Sums of squares of integers
/ Moreno, Carlos J. ; Wagstaff, Samuel S. Jr.
-Boca Raton FL : Chapman and Hall;CRC press, 2006. - xi, 354 p. ; 24 cm
ISBN 9781584884569