Richard D. Roberts and Patrick C. Kyllonen, “Morning-Eveningness and Intelligence: Early to Bed, Early to Rise Will Make You Anything but Wise!” Personality and Individual Differences 27 (1999): 1123–1133; Davide Piffer et al., “Morning-Eveningness and Intelligence Among High-Achieving US Students: Night Owls Have Higher GMAT Scores than Early Morning Types in a Top-Ranked MBA Program,” Intelligence47 (2014): 107–112.