Before revision: cite book|author1=Lars Bäckman|author2=Lars Nyberg|title=Memory, Aging and the Brain: A Festschrift in Honour of Lars-G ran URL August 2009|publisher=Psychology Press|isbn=978-0-203-86666-5|page=41 The scientifc evidence for its existence is contended.
After revision: The scientifc evidence for its existence is contended.