1. El Método Lexiway (Lexiway website). Available athttp://academialexiway.com/academia-ingles/metodo-academia-ingles.html accessed 28 November2016
2. Duolingo website. Available athttps://www.duolingo.com/ accessed 28 November2016
3. Babbel website. Available athttps://www.babbel.com/ accessed 28 November2016
4. Busuu website. Available athttps://www.busuu.com/ accessed 28 November2016
5. ‘Duolingo effectiveness study’. Final Report 2012. Available athttp://static.duolingo.com/s3/DuolingoReport_Final.pdf accessed 28 October 2016