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Dekkers, O M; von Elm, E; Algra, A; Romijn, J A; Vandenbroucke, J P (2010). How to assess the external validity of therapeutic trials: a conceptual approach. International journal of epidemiology, 39(1), pp. 89-94. Oxford: Oxford University Press 10.1093/ije/dyp174
von Elm, E; Altman, D G; Egger, M; Pocock, S J; Gøtzsche, P C; Vandenbroucke, J P (2008). [The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement: guidelines for reporting of observational studies]. Internist, 49(6), pp. 688-693. Heidelberg: Springer-Verlag 10.1007/s00108-008-2138-4
