1. Brüdern, J., Sums of squares and higher powers, J. London Math. Soc., 35(2), 1987, 233–243.
2. Brüdern, J. and Kawada, K., The asymptotic formula in Waring’s problem for one square and seventeen fifth powers, Monatshefte fr Mathematik, 162(4), 2011, 385–407.
3. Hardy, G. H. and Littlewood, J. E., Some problems of “Partitio Numerorum”, I, a new solution to Warings problem, Göttinger Nachrichten, 1920, 33–54,
https://doi.org/eudml.org/doc/59073
.
4. Hardy, G. H. and Littlewood, J. E., Some problems of “Partitio Numerorum”, VI, further researches in Warings problem, Math. Z., 23, 1925, 1–37.
5. Hua, L. K., Additive Theory of Prime Numbers, 13, Amer. Math. Soc., Providence, RI, 1965.