Public
Being close to an event doesn't make a source complete. The Library of Congress notes that primary sources are often incomplete and short on context. It tells readers to find other sources that support or contradict them. Wineburg's 1991 study of historians named this habit corroboration, meaning comparing documents with one another. He described it alongside sourcing (who made the document and why) and contextualization (when and where it was made). When a note rests on a primary source, cite what you checked it against.