1. Nowak D, Jörres RA, Rüther T: E-cigarettes—prevention, pulmonary health, and addiction. Dtsch Arztebl Int 2014; 111: 349–55
2. Deutsches Krebsforschungszentrum (DKFZ) (ed.): Tabakatlas. Deutschland 2015. www.dkfz.de/de/tabakkontrolle/download/Publikationen/sonstVeroeffentlichungen/Tabakatlas-2015-final-web-dp-small.pdf (last accessed on 14 September 2016).
3. Patent: Smokeless non-tobacco cigarette). (last accessed on 14 September 2016).
4. Consumer Advocates for Smoke Free Alternatives Association: E-cigarette history. www.casaa.org/E-cigarette_History.html (last accessed on 14 September 2016).
5. European Commision: Special eurobarometer 429“attitudes of Europeans towards tobacco and electronic cigarettes.” 2015.