All the following are authorized sources for derivative classification except:

Derivative classification involves using existing classified information to create new classified documents. Authorized sources for this process provide reliable and validated information that can be used to maintain the integrity of classified material.

Unconfirmed sources are not considered authorized because they lack the validation required for use in derivative classification. They may provide information that is speculative or unverified, which risks unintentionally disclosing sensitive information or compromising the security of classified material.

In contrast, the other options—observations from classified briefings, technical manuals, and approved reports—are recognized as legitimate sources. These sources have undergone the necessary review processes to ensure that any information derived from them is both accurate and appropriately classified. Using confirmed and approved sources helps ensure compliance with information security protocols.