On Factor Tables, with an Account of the Mode of Formation of the Factor Table for the Fourth Million [Book] James Whitbread Lee Glaisher (1878)
On the diameter of sets of almost powers B. M. M. de Weger, C. E. van de Woestijne (1999) Acta Arithmetica
On the distribution of analytic | Sh | values on quadratic twists of elliptic curves. Quattrini, Patricia L. (2006) Experimental Mathematics