Model tax convention commentaries guide treaty interpretation and serve as authoritative non binding aids when treaty text mirrors the model. Commentaries to the OECD and UN Model Tax Conventions serve as authoritative interpretive aids for DTAAs: the OECD Model emphasizes residence-based taxation while the UN Model emphasizes source-based taxation; both commentaries explain technical expressions and are persuasive in court decisions. They are not binding on Contracting States but may be relied upon where states adopt model wording without change, and the UN Commentary adapts OECD analysis to developing-country contexts.