And I think this bears repeating for you c&p:
4. Defining questions
When evaluating primary or secondary sources, the following questions might be asked to help ascertain the nature and value of material being considered:
How does the author know these details (names, dates, times)? Was the author present at the event or soon on the scene?
Where does this information come from—personal experience, eyewitness accounts, or reports written by others?
Are the author's conclusions based on a single piece of evidence, or have many sources been taken into account (e.g., diary entries, along with third-party eyewitness accounts, impressions of contemporaries, newspaper accounts)?
Ultimately, all source materials of whatever type must be assessed critically and even the most scrupulous and thorough work is viewed through the eyes of the writer/interpreter. This must be taken into account when one is attempting to arrive at the 'truth' of an event.