A Positive Definite Binary Quadratic Form as a Sum of Five Squares of Linear Forms (Completion of Mordell's Proof)
Bulletin Polish Acad. Sci. Math. 61 (2013), 23-26 MSC: Primary 11E25. DOI: 10.4064/ba61-1-3
The paper completes an incomplete proof given by L. J. Mordell in 1930 of the following theorem: every positive definite classical binary quadratic form is the sum of five squares of linear forms with integral coefficients.