The zeros of Riemann's Zeta-Function on the critical line G.H., and J.E. Littlewood Hardy — 1921 Mathematische Zeitschrift
Some Problems of "Partitio numerorum": II Proof that every large number is the sum of at most 21 biquadrates G.H., and J.E. Littlewood Hardy — 1921 Mathematische Zeitschrift
Some problems of "Partitio Numerorum": IV The singular series in Waring's Problem and the value of the number G (k) Hardy G.H. and J.E. Littlewood — 1922 Mathematische Zeitschrift