Journals specializing in ancient philosophy include:
Journal of Indian Philosophy
Phronesis
Plato
Articles on ancient philosophy may also be found in journals with a broader theme. Try searching your topic on JSTOR or the EBSCOhost databases. See the journal articles tab for more resources.
It's usually best to start with a keyword search, but subject headings applied to relevant books can help to refine your results. Open the item record of a book that interests you. Scroll down to the clickable subject headings, and run another search to explore similar books.
You can also browse the headings associated with a particular topic as a way of getting started with your research.
Titles on ancient philosopy are cataloged with the broad subject heading Philosophy, Ancient.
Some examples are:
Ancient philosophy: essential readings with commentary
(View table of contents online)
GENERAL B111 .A534 2008
The Internet Classics Archive
Online works from various authors, mostly western.
Erratic Impact: Ancient Philosophy
Listing of important people and events in ancient philosophy, with links to suggested reading and some online resources. A starting point for brainstorming topics and sources.