The contents of the codices were written in the Coptic language. The best-known of these works is probably the Gospel of Thomas, of which the Nag Hammadi codices contain the only complete text. After the discovery, scholars recognized that fragments of these sayings attributed to Jesus appeared in manuscripts discovered at Oxyrhynchus in 1898 (P. Oxy. 1), and matching quotations were recognized in other early Christian sources. The written text of the Gospel of Thomas is dated to the second century by most interpreters, but based on much earlier sources. The buried manuscripts date from the 3rd and 4th centuries.