Regulation and Integration in the Mammalian Circadian System.
Progress in Brain Research 1996; 111:191-203
M R Ralph, M W Hurd, J Takeuchi, L Melo, A Mathur, D A Golombek
"In mammals the principal pacemaker that generates circadian rhythms is located in the suprachiasmatic nucleus (SCN) of the hypothalamus, and light information transmitted from the retina to the SCN entrains this clock." Abstract