Classification of post COVID-19 condition symptoms: a longitudinal study in the Belgian population, Nayani, Sarah, Castanares-Zapatero Diego, De Pauw Robby, Van Cauteren Dieter, Demarest Stefaan, Drieskens Sabine, Cornelissen Laura, Devleesschauwer Brecht, De Ridder Karin, Charafeddine Rana, et al. , BMJ Open, Jun-10-2023, Volume 13, Issue 10, (2023)