The relationship between electron delocalization, potential energy lowering, and chemical stability is a fundamental tenet of quantum chemistry and molecular bonding covered extensively in standard textbooks; no specific citation is needed.
The claim represents foundational chemical physics taught in introductory chemistry and physics curricula. Electron delocalization (such as resonance or conjugation) spreads electron density over a larger spatial region, which decreases kinetic and potential energy contributions according to quantum mechanical principles, thereby conferring thermodynamic stability. Because this is a definitional and universally accepted chemical principle, it is categorized as common knowledge requiring no citation.