Jia, Chao Hua. "The distribution of square-free numbers", Science in China Series A: Mathematics36:2 (1993), pp. 154–169. Cited in Pappalardi 2003, A Survey on k-freeness; also see Kaneenika Sinha, "Average orders of certain arithmetical functions", Journal of the Ramanujan Mathematical Society21:3 (2006), pp. 267–277.
Jia, Chao Hua. "The distribution of square-free numbers", Science in China Series A: Mathematics36:2 (1993), pp. 154–169. Cited in Pappalardi 2003, A Survey on k-freeness; also see Kaneenika Sinha, "Average orders of certain arithmetical functions", Journal of the Ramanujan Mathematical Society21:3 (2006), pp. 267–277.