See M. N. Dhalla, Zoroastrian Theology (1914, repr. 1972) and History of Zoroastrianism (1938, repr. 1963); R. C. Zaehner, The Dawn and Twilight of Zoroastrianism (1961); M. Boyce, Zoroastrians (1986); M. Farhang, The Zoroastrian Tradition (1988). The Manual of Discipline in the Dead Sea Scrolls is believed to reflect Zoroastrian influence. See also bibliography under Zoroaster.