What is the caste system (and jati), and who are Aryans, Dravidians, Brahmans, and dalits (Untouchables)? 

4 pages long, 3 sources from any legitimate mainstream book, journal article, periodical, or newspaper (in that order of importance).  No dictionaries or encyclopedias, especially Wikipedia. cite a source using the APA Style for anything that is not common knowledge, let alone if you quote from it. Use standard formatting (double-spaced, 12-point Times or Times New Roman, normal margins, page numbering, etc.). Do not do a Title Page or sub-headings. Do a Works Cites section (which will not count for length).