Complex sentence: According to Abbas Milani's book' The Persian Sphinx', he was the mentor of the Prime Minister Amir-Abbas Hoveida who referred to him as "arbab" (the boss).
Split into simpler sentences: According to Abbas Milani's book' The Persian Sphinx', he was the mentor of the Prime Minister Amir-Abbas Hoveida. Hoveida referred to him as "arbab" (the boss).