When conducting historical research, it's important to use both primary and secondary sources. Think of it as being like reading both a diary of a person and a biography of them. From the diary (a primary source), you can find out what they thought of things they'd done and how they felt about it in the moment. From the modern-day biography (a secondary source) you can find out how the outside world saw them at the time, or how the world sees them today. Both can tell you interesting things about that person on their own, but together you get a more rounded picture.
A primary source can be:
A secondary source can be:
Multidisciplinary databases are recommended more for topics with a contemporary dimension than historical topics