Salaamon Alaikom dear Sister Maryam and welcome!
Thank you for your question. I think the following links might be useful in this regard:
1-http://www.al-islam.org/shiite-encyclopedia-ahlul-bayt-dilp-team/tawassul-resorting-intermediary.
2-http://www.al-islam.org/al-imam-al-mahdi-just-leader-humanity-ayatullah-ibrahim-amini.
3-http://www.al-islam.org/shiite-encyclopedia-ahlul-bayt-dilp-team/necessity-existence-imam-al-mahdi.
4-http://www.al-islam.org/shiite-encyclopedia-ahlul-bayt-dilp-team/special-specifications-imam-al-mahdi.
5-http://www.al-islam.org/shiite-encyclopedia-ahlul-bayt-dilp-team/sunni-documentation-imam-al-mahdi.
Fi- AmaneAllah
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