|Britannica Junior Encyclopedia for Boys and Girls. Encyclopedia Britannica, Inc., 1976|
|Edgar McInnis. The North American Nations. Toronto: J.M. Dent & Sons (Canada) Ltd., 1963.|
|1957 Encyclopedia Year Book. The Story of Our Time. The Grolier Society, Inc.|
According to the Wikipedia entry,
"A controversy also developed between the United States and Canada over the cleanup of deactivated Canadian DEW Line sites. The stations had produced large amounts of hazardous waste that had been abandoned in the high Arctic. Especially damaging were the large quantities of PCBs. While the United States insisted that it was Canada's responsibility to clean up the sites they had managed, the Canadian government disagreed. In 1996, an agreement was reached that saw the United States contribute $100 million to the estimated $600 million cleanup effort. The cleanup is now underway, site by site."