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\bibitem{Kuepper_etal2011} Kuepper, R., van Os, J., Lieb, R., Wittchen, H. - U., H{\"o}fler, M., \& Henquet, C. (2011). Continued cannabis use and risk of incidence and persistence of psychotic symptoms : 10 year follow-up cohort study. \textit{British medical journal}, \textit{342}, 8.

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