Answered By: University Libraries Last Updated: Jan 05, 2018 Views: 5
I would recommend starting at the English 210 research guide: http://libguides.usd.edu/content.php?pid=92383&sid=2590559
The four databases listed are a good starting point.
You may not find critiques about those specific poems, but more likely about the author, their themes, etc.
Search for the authors' names in quotes: "Dylan Thomas" for example, and search each author separately (you're unlikely to find articles that have already compared them.
You can also try the Academic Search Premiere database.