1. R. Baer, Factorization ofn-soluble andn-nilpotent groups. Proc. Amer. Math. Soc.4, 15?26 (1953).
2. F. W. Barnes, Forcing sets of exponents in groups. Problem E 2411, MAA Monthly81, 410 (1974).
3. H. E. Bell, On some commutativity theorems of Herstein. Arch. Math.24, 34?38 (1973).
4. H. E. Bell, On the power map and ring commutativity. Canad. Math. Bull.21, 399?404 (1978).
5. H. E. Bell, On power endomorphisms of the additive group of a ring. Math. Japon.29, 419?426 (1984).