Sources of variance in daily physical activity levels in the seasonal variation of blood cholesterol study.
Matthews CE, Hebert JR, Freedson PS, Stanek EJ, Merriam PA, Ebbeling CB, Ockene IS. Sources of variance in daily physical activity levels in the seasonal variation of blood cholesterol study. Am J Epidemiol. 2001 May 15; 153(10):987-95.