Kopparapu et al. "Habitable Zones Around Main-Sequence Stars: Dependence on Planetary Mass"
http://arxiv.org/abs/1404.5292Wider HZ for more massive planets.
Including an updated online calculator giving values for 5 M
E and 0.1 M
E planets
here-----
Yang et al. "Strong Dependence of the Inner Edge of the Habitable Zone on Planetary Rotation Rate"
http://arxiv.org/abs/1404.4992Slowly-rotating planets can be more habitable due to increased cloud coverage. Some potentially-interesting implications for Venus.