1. C. Bauer and Y.H. Wang, Hua’s theorem for five almost equal prime squares, Arch. Math., 86:546–560, 2006.
2. L.K. Hua, Some results in the additive prime number theory, Q. J. Math., 9:68–80, 1938.
3. J.Y. Liu, G.S. Lü, and T. Zhan, Exceptional sums over prime variables in short intervals, Sci. China, Ser. A, 49(4):448–457, 2006.
4. J.Y. Liu and T. Zhan, Estimation of exponential sums over primes in short intervals. II, in Analytic Number Theory, Proceedings of a Conference in Honor of Heini Halberstam, Vol. 2, Birkhäuser, Boston, 1996, pp. 571–606.
5. J.Y. Liu and T. Zhan, On sums of five almost equal prime squares, Acta Arith., 77:369–383, 1996.