Dear Rafael,
Thanks for your question. DOAJ doesn't currently support multilingual articles, unfortunately. We have it on our list of things to develop, however.
In the meantime, you can submit as many languages as you like in the one tag, separated by a delimiter, such as |. This is a workaround and not the solution but until we can support more than one langue in titles, abstracts etc then it's the best fix.
Let me know if you have any more questions.
Best wishes, Dom
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Dom Mitchell
DOAJ Operations Manager