You can view your Search History at anytime by clicking Search History underneath the search boxes. This is only for your current browser session! Your History will open in a pane above your search results. Close it by clicking Search History again.
If you ran two (or more) separate searches you want to combine (out of the Headings, for example), this can be done using your Search History. Anything currently in the search boxes will be added, so make sure those are empty if that is not your intention. Select the searches you want to combine and click Search with AND to look for both.
You can also use the Search with OR option to find either one, the other or both.
Print Search History is available in upper left. You are required to turn in your printed search history with your paper. Note you can also go back to results from previous searches and edit previous searches from this screen.