APA format is used by researchers in the social sciences field, and requires in-text citations as well. It ends the paper with a “references” page, and may also have section headers between body paragraphs.
If you find one really awesome book or journal that fits your topic perfectly, try looking in the works cited/bibliography/reference list at the end of it. This should contain many more books and journals that are about your topic as well.
Whenever possible, look for peer-reviewed empirical research. These are articles or books written by experts in your field of interest, whose work has been read and vouched for by other experts in the same field. These can be found in scientific journals or via an online search.
The introduction is, in many respects, the conclusion written in reverse: start by generally introducing the larger topic, then orient the reader in the area you’ve focused on, and finally, supply the thesis statement. Avoid repeating exact phrases that you already used in the conclusion.