I submitted a paper to a scientific conference, which was not yet published at that time. In the meantime, my paper has been published in a journal.
But in the last days I received the confirmation that my article was accepted for this conference. The website for this conference states that authors are invited to submit their article to a number of journals after presentation. I have read in the case of other other conferences that already published articles are not accepted. Unfortunately, the conference website does not provide any further information.
Now my question is: am I allowed to present an already published paper at a conference?