According to the Polish wiki page about Urka, the Urkas group has been described by Gustaw Herling Grudzinski in the novel "A World Apart":
A World Apart: The Journal of a Gulag Survivor (Polish: Inny świat: zapiski sowieckie)[1] is a memoir written by Gustaw Herling-Grudziński, combining various literary genres: novel, essay, psychological portrait, as well as sociological and political dissertation. It was first published in 1951 in London in the English translation by Andrzej Ciołkosz.[2] In the Polish language, the book was first published in London in 1953, then in Poland by the underground press in 1980, and officially in 1988.
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