Hello,

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.