In the 1630s, Grotius was engaged in extensive reading of patristic texts. From his involvement with these texts come the numerous and sometimes extensive quotations from patristic texts in the Annotata of De veritate religionis Christianae, which accompanied the work starting in 1640. Grotius was particularly interested in the apologetic literature of the ancient Church, which can also be seen in his correspondence. Strikingly, Grotius cites individual passages from texts that had not yet appeared in print, which he could only have learned of from the circle of those who, in 1630s Paris, were working to produce editions of various Greek texts. The texts in question are Cyril of Alexandria, Contra Julianum, and the letter of Barnabas. Grotius had received a handwritten copy of the Barnabas letter, which he later bound into his notebook amid excerpts of patristic texts. This shows the high level of detail at which Grotius knew the patristic texts, and how he moved in the intellectual circles of Paris.