That temperatures typically drop after the passage of a cold storm front is a matter of common meteorological observation and definition, requiring no formal citation.
The claim states a fundamental, defining characteristic of cold fronts—that they bring cooler air—which is a matter of everyday meteorological observation and basic physical definition (common knowledge). Papers [1] and [9] also note temperature drops following cold fronts as part of their observational contexts, but citations are not strictly required for such basic textbook facts.