Odd Repdigits to Small Bases are Not Perfect. - Kevin A. Broughan; Qizhi Zhou (Integers, 2012)

Improving the Chen and Chen Result for Odd Perfect Numbers. - Kevin A. Broughan; Daniel Delbourgo; Qizhi Zhou (Integers, 2013)

On the Ratio of the Sum of Divisors and Euler's Totient Function II. - Kevin A. Broughan; Qizhi Zhou (J. Integer Seq., 2014)