Afnan, Ruhi Muhsen. Zoroaster's Influence on Greek Thought. New York, N.Y.: Philosophical Library, 1965, 436 p.
Analysis of the degree to which Zoroaster and his doctrines influenced the thinking of various Greek philosophers and schools of philosophical thought, including the Milesian school; the Orphic and Pythagorean mystics; the Eleatics; Heraclitus; Protagoras; Socrates; and Plato.
Boyce, Mary. A History of Zoroastrianism. Leiden: E. J. Brill, 1975, 347 p.
Historical analysis of the religious background from which Zoroastrianism arose; Zoroaster and his doctrines; and the “prehistoric period” of faith.
Carter, George William. Zoroastrianism and Judaism. New York, N.Y.: AMS Press, 1918, 116 p.
Studies the way in which Zoroaster and his spiritual doctrines influenced Judaism's conception of deity, heaven, morals and ethics, and the afterlife.
Dawson, Miles Menander. The Ethical Religion of Zoroaster. New York, N.Y.: AMS Press, 1931, 271 p.
Discussion of Zoroaster's teachings as an ancient and “most accurate” ethical code of conduct.
Insler, S. The Gathas of Zarathustra. Leiden: E. J. Brill, 1975, 387 p.
Offers an introduction to Zoroaster's Gathas; a translation of the text; commentary on the text; and a glossary to the Gathas.
Jackson, A. V. Williams. Zoroaster: The Prophet of Ancient Iran. New York, N.Y.: Macmillan, 1899, 314 p.
Reviews what is known about Zoroaster's life and recounts the legends of his birth that sprung up after Zoroaster's death; discusses events contemporary with Zoroaster's life; and surveys the beliefs of Zoroaster as presented in the Gathas.
Klima, Otakar. “The Date of Zoroaster.” Archiv Orientalni 27, No. 4 (1959): 556-64.
Examines possible sources of dating Zoroaster's life that lie outside Zoroastrian tradition.
Moulton, James Hope. Early Zoroastrianism. London, 1913, 463 p.
Contains a modern English translation of the Gathas as well as commentaries on Zoroaster's doctrines and the development of the religion.