Evidence, the function of the historian is to show, interpret and give the clarity necessary to tell the story with real and confirmed facts and this generates a great difficulty, because many times the information was lost in the course of time, the information is ambiguous and manipulated That is why you must carry out an excellent investigation.
popular themes. Historical importance, this is a very important issue, since if it is a fact with little importance the sources of information and research support will not have a social significance