This is a direct restatement of the thermodynamic definition of entropy change (dS = dQ/T), where a lower absolute temperature T results in a larger entropy increase for a given increment of added heat dQ. Therefore, no citation is needed.
The claim follows directly from the classical definition of thermodynamic entropy change, dS = dQ/T. Adding a given quantity of heat (dQ) at a lower temperature (T) yields a larger change in entropy (dS) than doing so at a higher temperature. Because this is a fundamental textbook definition in thermodynamics, it is classified as common knowledge and requires no specific paper citation.