Vitamin C is naturally present in various shelf-stable and preserved foods, or can be stored for extended periods using appropriate techniques and technologies, making this claim common knowledge.
The claim that there are long-term storable dietary sources of vitamin C is a matter of everyday observation and general knowledge regarding preserved foods and vitamin C stability (such as in dehydrated foods, canned goods, and preserved fruits and vegetables). Therefore, no citation is needed and the claim is classified as common knowledge.