By the mid-20th century, Canadian writers were exploring national themes for Canadian readers. Authors were trying to find a distinctly Canadian voice, rather than merely emulating British or American writers. Canadian identity is closely tied to its literature. The question of national identity recurs as a theme in much of Canada's literature, from Hugh MacLennan's "Two Solitudes" (1945) to Alistair MacLeod's "No Great Mischief" (1999). Canadian literature is often categorized by region or province; by the socio-cultural origins of the author (for example, Acadians, indigenous peoples, LGBT, and Irish Canadians); and by literary period, such as "Canadian postmoderns" or "Canadian Poets Between the Wars".