Niven, Ivan (1971). "A Proof of the Divergence of Σ 1/p". The American Mathematical Monthly. 78 (3): 272–273. doi:10.1080/00029890.1971.11992740.. The half-page proof is expanded by William Dunham in Euler: The Master of Us All, pp. 74-76.
Lord, Nick (2015). "Quick proofs that certain sums of fractions are not integers". The Mathematical Gazette. 99: 128–130. doi:10.1017/mag.2014.16. S2CID123890989.
Lord, Nick (2015). "Quick proofs that certain sums of fractions are not integers". The Mathematical Gazette. 99: 128–130. doi:10.1017/mag.2014.16. S2CID123890989.