Lipsius, Zur Quellenkritik des Epiphanios, 1875; also Die Quellen der ältesten Ketzergeschichte, 1875.
Harnack, Zur Quellenkritik d. Gesch. d. Gnostic, 1873 (continued i. D. Ztschr. f. d. hist. Theol. 1874, and in Der Schrift de Apellis gnosi monarch. 1874).
Of Gnostic writings we possess the book Pistis Sophia, the writings contained in the Coptic Cod. Brucianus, and the Epistle of Ptolemy to Flora; also numerous fragments, in connection with which Hilgenfeld especially deserves thanks, but which still require a more complete selecting and a more thorough discussion (see Grabe, Spicilegium T. I. II. 1700. Heinrici, Die Valentin. Gnosis, u. d. H. Schrift, 1871).
On the (Gnostic) Apocryphal Acts of the Apostles, see Zahn, Acta Joh. 1880, and the great work of Lipsius, Die apokryphen Apostelgeschichten, I. Vol., 1883; II. Vol., 1887. (See also Lipsius, Quellen d. röm. Petrussage, 1872).
Neander, Genet. Entw. d. vornehmsten gnostischen Systeme, 1818.
Matter, Hist. crit. du gnosticisme, 2 Vols., 1828.
Baur, Die Christl. Gnosis, 1835.
Lipsius, Der Gnosticismus, in Ersch. und Gruber's Allg. Encykl. 71 Bd. 1860.
Moeller, Geschichte d. Kosmologie i. d. Griech. K. his auf Origenes. 1860.
King, The Gnostics and their remains, 1873.