Our brothers regularly ask us to give them reference regarding mourning (Matam), I request you humbly to please provide me with some valid references so that we can have references to clear their doubts.

The best book with all the proofs is this one and is available via amazon

Commemorating the Mourning Rights of Imam al-Husayn https://smile.amazon.com/dp/1514298619/ref=cm_sw_r_cp_api_glt_fabc_6802V0FJW0Y9PBJBNYX9

Also i did a lecture on it 6 years ago