Low temperatures inducing a withdrawal reflex is a basic physiological observation and a matter of everyday knowledge, requiring no formal citation.
The claim that low temperatures can induce a withdrawal reflex is a standard, observable physiological truism (like pulling one's hand away from ice or cold water). Under Step 0 of the instructions, statements that are trivially true by direct everyday observation are classified as COMMON_KNOWLEDGE, meaning no citation is needed and paper indices are left empty.