1. The Prophet Muhammad (SAWA) has mentioned that his successors will be twelve, all of them from Quraish (Bukhari, Hadeeth 6682) and from Bani Hashim (al-Qondoozi, in Yanabee' al-Mawaddah, Vol.2, Hadeeth 908).

2. The Prophet (SAWA) informed about the names of the twelve Imams starting with Imam Ali (AS), them Imam Hasan, then Imam Husain, then Imam Ali Zainul Abideen, then Imam Muhammad Al-Baqir, then Imam Jafar Al-Sadiq (AS), then Imam Musa Al-Kadhim, then Imam Ali Al-Redha, then Imam Muhammad Al-Jawad, then Imam Ali Al-Hadi, then Imam Hasan Al-Askari, then Imam Al-Mahdi (Peace and blessings upon all of them).

3. Every Infallible Imam has informed his sincere followers about the next Imam after him. These statements are studied and been confirmed by all our most prominent scholars.

4. It is impossible for any one to claim that he is the Imam if he is not the real Imam, as the Shia in every age have seen from the Imam of their time the maximum knowledge and maximum piousness and miraculous phenomena  which prove that he is one of the the twelve successor of the Prophet (SAWA).

5. There is a very good book in this regard called Ethbaat al-Hudaat إثبات الهداة complied by Al-Hurr Al-Aamily in five volumes, containing authentic Hadeeths about the Imamate of the twelve Imams (AS).

Wassalam.