 Quadratic Residues by Ben Lynn

Online text: crypto.stanford.edu/pbc/notes/numbertheory/qr.html

By Ben Lynn. Stanford hosts the author's PBC Notes; it is not an institutional author. The inspected page is undated.

Cited passages: “Quadratic Residues”, opening definition and Euler criterion discussion; “The Legendre Symbol”, three values, odd-prime restriction, multiplication and square factors. The opening square-residue convention includes zero.