The Christian Classics Ethereal Library is a great place to look, as it is an online collection of primary writings from early Christian sources. You can search here by author or by title.
Another good database for this is Loeb Classical Library, which contains many primary sources from both early Christian and classical literature sources. You can access this resource here.
The JFL offers a webinar specifically on this subject which you can access here: https://watch.liberty.edu/media/t/1_mvebwybw/74370641
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