There are many archives and libraries throughout the world that hold important collections of primary documents. The Howard Gotlieb Archival Research Center at Boston University is one of them. One important source for finding archival collections in the United States is the National Union Catalog of Manuscript Collections. ArchiveGrid is another resource for finding archival material in the United States and worldwide. The National Archives (UK) provides records from the National Archives and from over 2,500 other archives in the UK. Archives Portal Europe provides access to information about archival material in various European countries. One can also search for archival material in Worldcat by using Advanced Search and limiting by format to Archival Material.