On the congruence f(x) + g(y) + c ≡ 0 (mod xy) (completion of Mordell's proof)
A. Schinzel (2015)
Acta Arithmetica
Similarity:
Assertions on the congruence f(x) + g(y) + c ≡ 0 (mod xy) made without proof by Mordell in his paper in Acta Math. 88 (1952) are either proved or disproved.