United States Census, 1920," index and images, FamilySearch (https://familysearch.org/pal:/MM9.1.1/MX17-HV9 : accessed 05 Oct 2014), Klaus Sieswerda, Marlborough Ward 5, Middlesex, Massachusetts, United States; citing sheet 6A, family 124, NARA microfilm publication T625, FHL microfilm 1820714.
"New England Petitions for Naturalization Index, 1791-1906," index and images, FamilySearch (https://familysearch.org/pal:/MM9.1.1/VXRZ-Z1Z : accessed 05 Oct 2014), Klaas Sieswerda, 1901; citing Massachusetts, NARA microfilm publication M1299, roll 107, National Archives and Records Service, Washington D.C.; FHL microfilm 1429777.