My book, Finding Alpha, highlights that conventional, and really any intuitive measure of risk, is at best unrelated to return. At worst, it is negatively related to returns.
Baker, Bradley, and Wurgler have a new, simple, paper on low risk equity portfolios.
This was pointed to me by Pim van Vliet, a quantitative researcher at Robeco. He has a nice presentation on Robeco's low risk portfolios here, and an SSRN paper on low-risk equity portfolios here.