Postmodern literature is hard to define and there is little agreement on the exact characteristics of it. Postmodern literature authors use many common themes and techniques to enhance their writing. Irony, pastiche, metafiction, and paranoia are just a few techniques that can be found in many postmodern literatures. Postmodernist writers explore this lack of authoritative truths in various forms of narrative techniques. They all reflect in various ways and measures the difficulties of mimetic reference to the actual world and its events, in such a way that they complex truth and knowledge. In their different ways postmodernist writers explore the difficulties of acknowledging and confronting the past be it private or public, and how this in turn conditions the perceptions of truth and reality. Examples are: Anais Nin's Under a Glass Bell (1944), William Gass's In the Heart of the Heart of the Country (1968), and Toni Morrison's Beloved (1987).