A source is a broad response to that question, if you see this in a question, the broad will be correct, let's say 89% of the time. Also, you could use the process of elimination, the others are basically discredited because they can be written by anyone. Rumor magazine article? Some random little girl's blog about something that happened thousands of years ago in a country that would be thousands of miles away if it still existed?(don't think so) Social Media Post, get real...
