An unverified source is ‘they say’ or ‘it appears’ or any of those vague responses that don’t pin down exactly who made the statement. If they are talking about scientific matters, it should be something that has been published in a reputable journal.

What you should not do is use Wikipedia (which is made up of opinions, not facts) or Yahoo responses, because you have no idea what the credentials are of the person responding. That includes me. I might be talking through my hat, but as long as I spell the words properly and use reasonable grammer, people think I know what I’m talking about. I usually do – but you have no way of knowing that.

So when you quote someone or refer to something, make sure there are references or credentials that would indicate that the information is correct and is verifiable.