Literature. The principal sources for the history of Trajan are Pliny the younger, Epistolce, especially lib. 10 and Panegynricus (ed. Gierig); Dion Cass. Hist. Rom. lib. 68 (unfortunately extant only in the extract by Xiphilinus); Aurel. Victor, Caes..13, 1 sq. and Epitome 13; Eutrop. 8:2; Orosius, 7:2 sq.; Tertull. Apologet. c. 1; Eüseb. Hist. Ecclesiastes 3, 12 sq.; Justin. Apologet. 1, 68; Rufinus, Hist. Ecc_4:9. See Ritterhusii Trajanus in Lucem Reproductus (1608); Mannert, Res Traj. Imp. ad . anu. Gestca (Norimb. 1793); Engel, Coment. de Expedit. Traj. ad Danub. et Origine Valachoarum (Vindeb. 1794); Wolf, Einermilde Stiftung Trajan's (Berl. 1808, 4to); Francke, Zür Gesch. Traj. u. seiner Zeifgenossen (Gustrow, 1837); Baldwin, Comment. et Edict. Vett. Princc. Rom. de Christianis (Hal. 1727, 4to); Bohmer, XII Dissertt. Juris Eccl. Ant. ad Plin. Sec. et Tertull. (2d ed. ibid. 1729), Martini, Persecutt. Christianorum sub Imp. Rom. (Onost. 1802, 4to); Kopke, De Statu et Condit. Christi sub Imp. Rom. Alterius post Christ. Scec. (Berol. 1828); Schröckh, Kirchengesch. 2, 320 sq.; Gieseler, Kirchengesch. 1, 134 sq.; and the monographs cited by Volbeding, Index Programmatum, p. 95, 98.Herzog, Real-Encyklop. s.v.; Smith, Dict. of Gr. and Rom. Biog. s.v. SEE PLINY.