Vitamin C Deficiency or Scurvy : https://en.wikipedia.org/wiki/Vitamin_C_deficiency
Vitamin C Megadosage : https://en.wikipedia.org/wiki/Vitamin_C_megadosage
Vitamin C and the common Cold : https://en.wikipedia.org/wiki/Vitamin_C_and_the_common_cold
Chemistry of Ascorbic Acid : https://en.wikipedia.org/wiki/Chemistry_of_ascorbic_acid
FYI, everybody knows how to search wikipedia.