It looks like you're using Internet Explorer 11 or older. This website works best with modern browsers such as the latest versions of Chrome, Firefox, Safari, and Edge. If you continue with this browser, you may see unexpected results.
A catalogue search initially brings back results in all available languages but can be limited to a particular language when conducting an Advanced Search. Simply select the intended language from the dropdown menu.
After completing a search, results can also be limited by language in the Results Refine by column under Languages.