These supplementary materials, Appendix 1, provide a dataset of digitized periodicals consulted including details on the repository, chronological coverage, and number of issues for each title. Issues of L’Avenir Savoyard, Le Concours Médical, Le Courrier de Domfront, Le Journal de la Belgique, Le Journal Illustré, Le Propagateur, and La Topographie du département du Gers, cited in the text, were consulted in physical form.