sentences:  The archive is extensive; it is the least studied area of the library collection.It contains Church documents of the 18 and 19th centuries, materials dating from the period of the Belarusian Democratic Republic (1918), archives of Belarusian organisations and personalities in exile.The history of the Library collection began with the establishment of the Belarusian Catholic Mission in London in 1947 and its move to Marian House on Holden Avenue in the following year.