Q. I am not quite sure whether our assignment will be based on the 4 articles (Harvard Business Review) only or based the three textbooks? What do "published articles" refer to exactly?
A. "Published Articles" refers to any article that is in the public domain; that is, any piece of written work (book, academic journal, magazine article, web site, etc) that you can cite in your essay as a source of information. Sections 3 and 4 of the handout for assignment 1 show how you should cite publications.
The sort of published articles that are most often used in this type of essay are the sort of books and journals that you can find via the Infothèque at Euromed. You will also find that the web page for each section of the course has links to a number of additional sources of information you could use.