You can find different resources online using databases purchased by the library. Databases are library tools that help you locate articles, book chapters, and more on a particular topic or author. Databases can vary by topic. Below are several resources that will be helpful for your research paper.
Use library search to find books and [some] articles. Books provide in depth information about any topic. Some books are primary sources - some are secondary. They provide more complete information to substantiate a topic or theory.
To find primary sources specifically, couple the topic of your subject heading with relevant subheadings that relate to the historical time period, place of origin, and item format of the materials that interest you. Use the Library Search for materials.
These "complex subjects" (containing more than one idea) have their own particular notation.