MedlinePlus on OTC: https://medlineplus.gov/overthecountermedicines.html
FDA on OTC: https://www.fda.gov/drugs/buying-using-medicine-safely/understanding-over-counter-medicines
How drugs transition from prescription to OTC: https://www.chpa.org/SwitchFAQs.aspx
The Heart Association on interactions between different drugs: https://www.heart.org/en/health-topics/consumer-healthcare/medication-information/medication-interactions-food-supplements-and-other-drugs
Medscape database on drugs, OTC's and herbal supplements: https://reference.medscape.com/drugs
OTC information data search: https://www.knowyourotcs.org/
Acetaminophen dose awareness website: https://www.knowyourdose.org/
How to store medicines safely in your home: https://www.upandaway.org/
Safe medicine use by children: https://www.healthychildren.org/English/safety-prevention/at-home/medication-safety/Pages/default.aspx
NIH on melatonin: https://www.nccih.nih.gov/health/melatonin-what-you-need-to-know
Psychology Today on melatonin: https://www.psychologytoday.com/us/blog/evidence-based-living/201803/the-evidence-melatonin-insomnia
Mayo Clinic on melatonin: https://www.mayoclinic.org/drugs-supplements-melatonin/art-20363071
Pretty extensive overview from Medical News Today on melatonin: https://www.medicalnewstoday.com/articles/232138#is-melatonin-safe-for-children
NIH on dietary supplements: https://www.nccih.nih.gov/health/using-dietary-supplements-wisely
USDA on dietary supplements: https://www.nutrition.gov/topics/dietary-supplements
FDA on dietary supplements: https://www.fda.gov/food/information-consumers-using-dietary-supplements/tips-dietary-supplement-users
USDA page filled with links to dietary supplement information: https://www.nal.usda.gov/fnic/general-information-and-resources-dietary-supplements
FTC on dietary supplements: https://www.consumer.ftc.gov/articles/0261-dietary-supplements