[Prererularl]

Harun Yahya has great works on Hazrat Mahdi (a.s.), and I advise all my Muslim brothers to follow up his works on the Internet on this issue.
First of all he is giving all sources and books that he uses quotations from. He always uses evidence for all his explanations.
He insists on using proofs because that is the only way to make "scientific" explanations on any subject.

So, I would suggest you to visit:

Mahdi According to Four Sunni Schools

The descent of Prophet ‘Isa (As) and the coming of the Mahdi are subjects “that cannot be denied” in the faith (itiqad) of the people of the people of the sunnah.
According to the beliefs of the people of the Sunnah (the Hanafi, Hanbali, Shafi’i and Maliki schools), the coming of the Mahdi, the descent from the skies of the Prophet ‘Isa (as) and his bestowing the role of imam on the Mahdi are all unquestionable tenets of faith. In this site you may find some trustworthy hadith regarding the coming of the prophet Isa (As) and the blessed Mahdi.

http://www.mahdiaccordingtofoursunnischools.com/