The claim that the total vapor pressure of immiscible liquids equals the sum of their individual vapor pressures is a standard thermodynamic principle (Dalton's Law of partial pressures applied to ideal immiscible mixtures) and requires no citation.
The provided claim is a fundamental physical law taught in basic chemistry regarding the behavior of completely immiscible liquids in closed systems. None of the retrieved papers specifically test, challenge, or focus on this textbook thermodynamic rule, making it common knowledge for which citations are unnecessary.