Do you know of an article on Florencio Sanchez's Barranca Abajo, which is also known as Retrogression in English?
If you're looking for articles, a great resource is Google Scholar. To use this tool, you simply go to the Google homepage and choose the link that says "more" at the top of the page (adjacent to links like "web," "images," etc.); a pull-down menu will appear, and you can click on "Scholar." Google Scholar is a database that searches for scholarly books and articles available on the internet. By just doing a quick search, I found this article on Sanchez from the journal Latin-American Theater Review:
By doing a search with the author's name and the title of the work, you should be able to find a number of good articles. Plus, the information you get when you search Google Scholar is often peer-reviewed and more reliable than standard internet content. Happy hunting!