"New York, Passenger Arrival Lists (Ellis Island), 1892-1924," index, FamilySearch (https://familysearch.org/pal:/MM9.1.1/JXWS-KMV : accessed 01 Oct 2014), Pieter Oppeioal, arrived at New York, 14 Apr 1896, on the Kensington; citing National Archives, Washington D.C.
"United States Census, 1920," index and images, FamilySearch (https://familysearch.org/pal:/MM9.1.1/MF9R-W9R : accessed 03 Oct 2014), Peter Oppewal, Sutton, Worcester, Massachusetts, United States; citing sheet 2A, family 29, NARA microfilm publication T625, FHL microfilm 1820748.