Proehl, Risa S. (March 2009). "2008 Oregon Population Report"(PDF). Population Research Center. Portland State University. p. 7. Archived from the original(PDF) on March 3, 2016. Retrieved May 5, 2009.
Proehl, Risa S. (March 2009). "2008 Oregon Population Report"(PDF). Population Research Center. Portland State University. p. 7. Archived from the original(PDF) on March 3, 2016. Retrieved May 5, 2009.