The statement that the Rayleigh-Jeans law accurately describes blackbody radiation at long wavelengths is a foundational, well-established physical principle, so no citation is needed.
The claim is a standard, undisputed physics law describing the classical limit of blackbody radiation at long wavelengths (low frequencies), which matches Planck's law in that specific limit. None of the retrieved papers directly address or test this specific law (they focus on medical/biological UV effects, photosynthesis, solar irradiance spectra, and Fermi-Pasta-Ulam-Tsingou models). Because this is a well-known scientific fact taught in introductory physics, it is classified as common knowledge.