Sum of two squares theorem - Wikipedia

Sums of four squares — AnhThu Nguyen

Lagrange's Four-Square Theorem, PDF, Number Theory

Lagrange's Four-Square Theorem -- from Wolfram MathWorld

PDF) Algebraic Consequences of Jacobi's Two- and Four-Square Theorems

FERMAT'S FOUR SQUARES THEOREM Several years ago, after

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

Discrete quantum computation and Lagrange's four-square theorem

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

PDF) Sums of four squares and Waring's Problem

Answered: The Modular Operation r mod m = r…