18 C.F.R. § 1301.65
(a) In accordance with Part 2 of Executive Order 13526 and directives of the Information Security Oversight Office, the incorporation, paraphrasing, restating or generation in new form of information that is already classified, and the marking of newly developed material consistent with the classification markings that apply to the source information, is derivative classification.
(b) Authorized individuals applying derivative classification markings shall:
(3) For information derivatively classified based on multiple sources, the authorized individuals shall carry forward: