Why expository? No research is required in this argument essay. However if you are using any source material include this in the Works Cited page and attempt to use correct in-text citations. For example, I might compare two different artist Poe and Maya Angelou and then claim one to be a more meaningful expression as demonstrated by tone, symbols, and point of view. If I use specifics examples from their poems then this should be in quotes and sourced in the Works Cited. However, if I try to convince the reader that everyone should develop a better understand and appreciate poetry and I use common knowledge to support this claim then no citations are needed.