Final answer:
The bottom of a classified document includes a classification marking with a 'Classified by' line indicating the classifying authority and a 'Derived from' line stating the source of the classified information.
Step-by-step explanation:
At the bottom of a classified document, you will typically find a section known as the classification marking. This section includes several important lines that denote the document's security level and provide guidance on how it should be handled. The 'Classified by' line indicates the authority or the official who classified the document. Another line, 'Derived from', references the source from which the classified information was derived or the previous authority for the classification, typically citing another classified document or a classification guide. Additionally, there is often a declassification date or event specified, which indicates when the document can be declassified.