[1] A. A. Klein, Annihilators of nilpotent elements, Int. J. Math.
Math. Sci. 21 (2005), 3517-3519.
[2] T. J. Laffey, Commutative subrings of periodic rings, Math. Scand.
39 (1976), 161-166.
[3] C. Lanski, Rings with few nilpotents, Houston J. Math. 16 (1992),
577-590.