The 13 project was a series of five edited volumes that were published annually from 2003-2007. The editors of the series were Klaus Petersen, Jørn Henrik Petersen and Lis Holm Petersen. The aim was to present academic research on Danish welfare state history in an accessible way to the Danish public. Each of the five books contains 13 essays written by prominent Danish researchers. The series was published by Syddansk Universitetsforlag and was well received by reviewers.