Which of the following is an authorized source for derivatively classifying documents?

A security classification guide is a recognized and authorized source for derivatively classifying documents because it provides specific guidance on how to apply classifications to particular information based on established criteria. These guides are carefully developed and vetted to ensure that they meet the necessary legal and procedural standards for classification. They outline clear rules and examples that assist individuals in understanding how to properly classify information, ensuring consistency, and adherence to federal classification policies.

In contrast, while a general information handbook might provide helpful context, it may not contain the specific authoritative guidance needed for classification decisions. A textbook on classification may offer general educational material and concepts but would not serve as an official source for classification purposes. A personal interpretation of regulations lacks the authority and cannot be relied upon for making classification determinations, as it represents an individual's subjective understanding rather than an established guideline.