Strain differences of the mouse's free-running circadian rhythm in continuous darkness.
D000818:Animals; D002940:Circadian Rhythm; D003624:Darkness; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008815:Mice, Inbred Strains / Q000502:physiology*; D009043:Motor Activity / Q000502:physiology*; D012146:Rest; D013045:Species Specificity