Muhammad Rida al-Muzaffar (Arabic: محمد رضا المظفر) was a Shia Marja', philosopher and jurist. His book in Islamic sciences is Usul al-Fiqh or the principles of jurisprudence written according to the thought school of Agha Shaykh Muhammad Hosein Isfahani, one of the Shia Marja's. Source: Wikipedia (en)