An Independent Quaternion Proof of Jacobi's Four Square Theorem

Solved Theorem 8.35 (Lagrange's Four-Square Theorem) If n is

PDF) Two refinements of Lagrange's four-square theorem

Lagrange's four-square theorem

Euler's four-square identity

PDF] New parametrization of $A^2+B^2+C^2=3D^2$ and Lagrange's four-square theorem

Lagrange's 4 Square Theorem using Python

Lagrange's Four Square Theorem

Solved Lagrange's four square theorem says every natural

number theory - The Four Square Theorem and Integral Apollonian Circle Packings, is there any connection? - Mathematics Stack Exchange

Lagrange's Four-Square Theorem Seen Using Polygons and Lines