https://www.ncbi.nlm.nih.gov/books/NBK562207/ 
https://pubmed.ncbi.nlm.nih.gov/20663066/ 
https://www.ncbi.nlm.nih.gov/books/NBK555990/#:~:text=Proteins%20serve%20as%20structural%20support,secondary%2C%20tertiary%2C%20and%20quaternary. 
https://pubmed.ncbi.nlm.nih.gov/7965456/
https://pubmed.ncbi.nlm.nih.gov/10423619/#:~:text=The%20recent%20national%20survey%20shows,Panel%20on%20Optimal%20Calcium%20Intake. 
https://pubmed.ncbi.nlm.nih.gov/20515554/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3936689/#:~:text=Vitamin%20A%20supplementation%20reduces%20child,vitamin%20A%20dose%20is%20administered. 
https://pubmed.ncbi.nlm.nih.gov/19887691/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3262613/ 
https://pubmed.ncbi.nlm.nih.gov/31203294/
https://en.wikipedia.org/wiki/Amino_acid