The physiological period length of the human circadian clock in vivo is directly proportional to period in human fibroblasts. oleh Lucia Pagani, Ekaterina A Semenova, Ermanno Moriggi, Victoria L Revell, Lisa M Hack, Steven W Lockley, Josephine Arendt, Debra J Skene, Fides Meier, Jan Izakovic, Anna Wirz-Justice, Christian Cajochen, Oksana J Sergeeva, Sergei V Cheresiz, Konstantin V Danilenko, Anne Eckert, Steven A Brown