Isensee, B., Hansen, J., Maruska, K., & Hanewinkel, R. (2014). Effects of a school-based prevention programme on smoking in early adolescence: A 6-month follow-up of the «Eigenstandig werden» cluster randomised trial. BMJ Open, 4(1), e004422. https://doi.org/10.1136/bmjopen-2013-004422