Before June 9, 2017, the search results page in OneSearch included a list of databases on the right-hand side of the page that was entitled "Additional Resources to Search."
That list of databases was replaced on June 9 by a shorter list of databases that appear as buttons under a heading entitled "Additional Resources." This list also appears on the right-hand side of the search results page, but you may need to scroll down the page in order to see the list.
You can click on any of the buttons (for LexisNexis, ProQuest ABI/INFORM, ProQuest Dissertations and Theses, or ProQuest News and Newspapers) to run a search in that database in a new window or tab. Note that your search results won't be added to your OneSearch results.