History of Dogma, Volume 1

by Adolf von Harnack

Mansel, The Gnostic heresies, 1875.

Jacobi, Art. "Gnosis" in Herzog's Real Encykl. 2nd Edit.

Hilgenfeld, Die Ketzergeschichte des Urchristenthums, 1884, where the more recent, special literature concerning individual Gnostics is quoted.

Lipsius, Art. "Valentinus" in Smith's Dictionary of Christian Biography.

Harnack, Art. "Valentinus" in the Encycl. Brit.

Harnack, Pistis Sophia in the Texte und Unters. VII. 2.

Carl Schmidt, Gnostische Schriften in koptischer Sprache aus dem Codex Brucianus (Texte und Unters. VIII. 1. 2).

Joël, Blicke in die Religionsgeschichte zu Anfang des 2 Christl. Jahrhunderts, 2 parts, 1880, 1883.

Renan, History of the Origins of Christianity. Vols. V. VI. VII.