Using bibliographies is another way of finding resources, distinct from using a database or search engine. Once you've found one useful article, book or dissertation, check its bibliography. Many of the items in that bibliography will in turn have their own bibliographies, and so on.
One disadvantage of this method is that it can only take you back in time, when you will often be more interested in the latest scholarship and analysis. Here are three ways round this:
1. when you find a quality, relevant resource, check what the author has published more recently. They may well have continued with similar research interests. See the page about finding works by a particular author.
2. In the case of many scholarly resources, you can use Google Scholar to see which later works have cited that resource. In the screenshot below, the highlighted Cited by link will take you to a list of more recent resources that have referenced the article in question:
For some resources, Summon will also list selected other items which cite that resource; but Google Scholar is many times more comprehensive.
3. Use Summon's advanced search (accessed from beneath the search box on the library homepage). The screenshot below shows how to run a search for works referring to Barthes's Camera Lucida that were published between 2012 and 2017: