Investigating the criteria for identifying Imam Mahdi(aj) referent before and after his advent

The issue of identifying and distinguishing Imam Mahdi real referent from false pretenders has existed since the presence of the infallible Imams. Having the rules and criteria that have been narrated from the infallible Imams for the recognition of Imam Mahdi (aj)real referent, among the pretenders of Mahdaviat can bring us to Imam Mahdi(aj) faster. Before the advent, criteria such as "Imam Mahdi physical characteristics, his genealogy, Imam's special knowledge and, most importantly, miracles" were mentioned to distinguish Imam Mahdi (aj) and to identify his real  referent after the advent, criteria such as "the  advent of Jesus Christ with him,  being  the legacies of earlier  prophets and executors with him, the appearing  actual signs of the advent and ultimately the internationality of Islam" have been presented.  Analyzing and documenting these criteria is what has been done in this paper.