Postmodern literature is a form of literature that is characterized by the use of metafiction, unreliable narration, self-reflexivity, intertextuality, and which often thematizes both historical and political issues. This style of experimental literature emerged strongly in the United States in the 1960s through the writings of authors such as Kurt Vonnegut, Thomas Pynchon, William Gaddis, Philip K. Dick, Kathy Acker, and John Barth. Postmodernists often challenge authorities, which has been seen as a symptom of the fact that this style of literature first emerged in the context of political tendencies in the 1960s. This inspiration is, among other things, seen through how postmodern literature is highly self-reflexive about the political issues it speaks to. Precursors to postmodern literature include Miguel de Cervantes’ Don Quixote (1605–1615), Laurence Sterne’s Tristram Shandy (1760–1767), Thomas Carlyle's Sartor Resartus (1833–34), and Jack Kerouac's On the Road (1957), but postmodern literature was particularly prominent in the 1960s and 1970s. In the 21st century, American literature still features a strong current of postmodern writing, like the postironic Dave Eggers’ A Heartbreaking Work of Staggering Genius (2000), and Jennifer Egan’s A Visit from the Goon Squad (2011). These works, however, also further develop the postmodern form. Sometimes the term "postmodernism" is used to discuss many different things ranging from architecture to historical theory to philosophy and film. Because of this fact, several people distinguish between several forms of postmodernism and thus suggest that there are three forms of postmodernism: (1) Postmodernity is understood as a historical period from the mid-1960s to the present, which is different from the (2) theoretical postmodernism, which encompasses the theories developed by thinkers such as Roland Barthes, Jacques Derrida, Michel Foucault and others. The third category is the “cultural postmodernism,” which includes film, literature, visual arts, etc. that feature postmodern elements. Postmodern literature is, in this sense, part of cultural postmodernism. Background Notable influences Late 19th and early 20th century playwrights whose work influenced the aesthetics of postmodernism include August Strindberg, Luigi Pirandello, and Bertolt Brecht. Another precursor to postmodernism was Dadaism, which challenged the authority of the artist and highlighted elements of chance, whim, parody, and irony. Tristan Tzara claimed in "How to Make a Dadaist Poem" that to create a Dadaist poem one had only to put random words in a hat and pull them out one by one. Another way Dadaism influenced postmodern literature was in the development of collage,