A measure of which newspapers are the most influential is an important foundation for any large-scale study of newspapers. A reliable measure of significance would allow studies to more strongly weigh articles in more influential papers. In this article, we use digital methods to create a partial citation index of a range of Dutch newspapers with a national circulation published in the period from 1920 to 1939. We find that using the digital archive of the National Library of the Netherlands (available through Delpher) enables us to find citations, but the problems of digitization make it impossible to create any index approaching comprehensiveness. Because source criticism – a crucial part of studying history – is made more difficult by digitization, it merits special notice in the digital age.