Literature may consist of texts based on factual information (journalistic or non-fiction), as well as on original imagination, such as polemical works as well as autobigraphy, and reflective essays as well as belles-lettres. Literature can be classified according to historical periods, genres, and political influences. The concept of genre, which earlier was limited, has broadened over the centuries. A genre consists of artistic works which fall within a certain central theme, and examples of genre include romance, mystery, crime, fantasy, erotica, and adventure, among others. Important historical periods in English Literature include Old English, Middle English, the Rennaisance, the 17th Century Shakesperean and Elizabethan times, the 18th Century Restoration, 19th Century Victorian, and 20th Century Modernism. Important political movements that have influenced literature include feminism, post-colonialism, psychoanalysis, post-structuralism, post-modernism, romanticism and Marxism.