How do you understand what’s an opinion and what’s well known?

Well known is an undeniable fact, so for instance I began in 1914 or that smoking is harmful…you wouldn’t need to provide a reference if you said, the capital of Canada is Ottawa, or that the Mona Lisa was painted by Leonardo da Vinci, or that World War. It’s effortlessly taken or verified for given. You will need to begin referencing once you move far from these generic suggestions to ones that identify the writers’…