You have found a film review, blog post, scholarly article, book, or some other type of print or online publication, and how you need to find the authority of the publications author.
Start with the publication itself. If it is scholarly, is there information indicating the author's academic affiliation or a short description about the author? If a book, is there an "About the Author" page to get you started?
Try searching in article databases, such as Compass (Search All), Academic Search Complete, Film & Television Literature Index, LexisNexis Academic, etc. to determine if any news or magazine articles have been written about the author.
You can also try an internet search to see if you can find any information on the author. If the reviewer or blogger is well known, then information about them may surface, so that you can determine which avenues to take. If the author is dead, you might find an obituary. If the author is associated with an academic institution, you may find the person's profile on a university's website.
As always, ask at the Research Center when you can't find the information you need for your research.