Vaughan, R. C.; Wooley, T. D. (1994), Further improvements in Waring's problem. II. Sixth powers, Duke Mathematical Journal, 76 (3): 683—710, doi:10.1215/S0012-7094-94-07626-6, MR1309326
Vaughan, R. C.; Wooley, T. D. (1994), Further improvements in Waring's problem. II. Sixth powers, Duke Mathematical Journal, 76 (3): 683—710, doi:10.1215/S0012-7094-94-07626-6, MR1309326