The public and secret negotiations between Constantius and Julian must be extracted, with some caution, from Julian himself (Orat. ad S. P. Q. Athen. p. 286), Libanius (Orat. Parent. c. 51, p. 276), Ammianus (xx. 9), Zosimus (1. iii. [c. g] p. 154), and even Zonaras (tom. ii. 1. xiii. [c. so] p. 20, 21, 22), who, on this occasion, appears to have possessed and used some valuable materials.