Because the Holy Roman Empire included territory in what is now a number of different countries over many centuries, scholars may use very different terminology when giving titles to their books. For instance, you might find sources about Germany that use:
early modern Germany
18th-century Germany (or other century)
Or use the name of a dynasty, such as Germany under the Ottonian dynasty
Names used to describe geographic areas can also change over time. I strongly suggest you talk to Dr. Gaydosh about what the most commonly used terminology for a region and/or time period is before you start researching. I can help, too, but she is the expert!
When I look for scholarly journal articles on history topics, this is the order I follow.
Historical Abstract and its cousin for American history (America: History and Life) pull articles from thousands of journals. If you haven't used it before, the videos below will help you understand how to set up a search and use limiters.
JSTOR is my second stop, because it doesn't include nearly as many journals as Historical Abstracts and America: History and Life. What is very useful about JSTOR is that you can search the full text of every article-- so it is great if you are looking for source that addresses a specific person, place, or thing. It also is interdisciplinary, including both history journals and journals from many other fields of study.
Library Search = the search box on the library homepage. It cross-searches dozens of databases, allowing for an extremely broad, interdisciplinary search. Click on the "Expand results beyond my library" option for an even more comprehensive search.
You can find books via the search box on library homepage.