Backman L, Small BJ, Wahlin Å, Larsson M : Cognitive functioning in very old age. In The Handbook of Aging and Cognition, 2nd ed., ed. by Craik FIM, Salthouse TA, 499-558, Lawrence Erlbaum Associates, Mahwah, NJ (2000) .
Cabeza R, Nyberg L : Imaging cognition II ; An empirical review of 275 PET and fMRI studies. J Cogn Neurosci, 12 (1) : 1-47 (2000).