https://www.colgate.com/en-us/oral-health/life-stages/adult-oral-care/how-acidic-foods-affect-teeth-and-which-to-avoid-1215
https://www.rd.com/health/conditions/mistakes-cause-tooth-decay-ruin-teeth/
http://www.webmd.com/oral-health/ss/slideshow-foods-stain-teeth
http://www.medicaldaily.com/does-tea-stain-your-teeth-6-surprising-foods-cause-yellow-teeth-320442