Euler's four-square identity - Wikipedia

LAGRANGE'S FOUR SQUARE THEOREM Theorems, Lagrange theorem, Number theory

Seatings and Sums of Squares

Lagrange's four-square theorem

Lagrange's four-square theorem - Wikiwand

GitHub - HechenHu/Four-Square_Representation: Using Rabin and Shallit's Algorithm to compute the four-square representation of a natural number as stated in Lagrange's Four-square Theorem.

Number Theory Sums of Squares Part 7.

Solved Lagrange's four square theorem says every natural

Discrete quantum computation and Lagrange's four-square theorem

Waring's Problem -- from Wolfram MathWorld

An Independent Quaternion Proof of Jacobi's Four Square Theorem: Zhang, Yuxuan: 9781719171571: : Books