Number of days, number of subjects, and sources of variation in longitudinal intervention or crossover feeding trials with multiple days of measurement.
Grunwald GK, Sullivan DK, Hise M, Donnelly JE, Jacobsen DJ, Johnson SL, Hill JO. Number of days, number of subjects, and sources of variation in longitudinal intervention or crossover feeding trials with multiple days of measurement. Br J Nutr. 2003 Dec; 90(6):1087-95.