Nagell, T. "Algebraic Congruences and Functional Congruences," "Algebraic Congruences to a Prime Modulus," "Algebraic Congruences
to a Composite Modulus," "Algebraic Congruences to a Prime-Power Modulus,"
and "Numerical Examples of Solution of Algebraic Congruences." §22,
24, and 26-28 in Introduction
to Number Theory. New York: Wiley, pp. 73-76, 79-81, and 83-93, 1951.