Henderson, David R. (June 2011). "Northern Exposure". Defining Ideas. Hoover Institution at Stanford University. Archived from the original on August 14, 2012. Retrieved August 12, 2012.
Henderson, David R. (June 2011). "Northern Exposure". Defining Ideas. Hoover Institution at Stanford University. Archived from the original on August 14, 2012. Retrieved August 12, 2012.