What are the different source of circumstantial evidence?

Actually, circumstantial evidence can be more convincing than eyewitness evidence. That is what the TV show CSI is all about. If we find the accused person's fingerprints at the murder scene, the...

Statements or information obtained indirectly or not based on firsthand experience by a person. Circumstantial evidence can include, in part, inferences about an event that was not seen. For example,...

secondary means you were there and saw the info primary mean you have heard it from somewhere else

Yes they are, and they should be cited accordingly.

Direct evidence are visible noticable changes. Indirect evidence is when you might not see the action happen but you do notice the results