https://aforisticamente.com/2015/11/03/frasi-citazioni-e-aforismi-su-arcobaleno/ http://www.meteoweb.eu/2013/04/larcobaleno-cose-come-si-forma-quando-e-perche-la-didattica-su-un-fenomeno-ottico-molto-suggestivo/197982/ https://www.google.com/search?q=immagini+arcobaleno&rlz=1C1ASUT_enIT539IT539&source=lnms&tbm=isch&sa=X&ved=0ahUKEwi1iZqay8rgAhUDLewKHfW6AwkQ_AUIDigB&biw=1366&bih=657