Bent's rule is a well-established chemical principle relating the s-character of hybrid orbitals to the electronegativity of attached substituents, and does not require citation.
The claim states Bent's rule, which is a foundational concept in chemistry taught in standard textbooks (describing how atoms direct s-character toward electronegative substituents). Because it is a textbook definition and fundamental chemical knowledge, it is classified as common knowledge and does not require supporting literature citations from the provided papers.