Here are some letters from the Canada Revenue Agency dealing with Article XXI (7) (formerly XXI(6)) of the Canada-US Tax Treaty.

 

2011 Letter from CRA on Article XXI of the Canada-US Tax Treaty 2011-040840

2010 Letter from CRA on Article XXI of the Canada-US Tax Treaty 2010-0380811E5

2009 Letter from CRA on Article XXI of the Canada-US Tax Treaty 2009-0322801E5

1999 Letter from CRA on Article XXI of the Canada-US Tax Treaty 9924098

1999 Letter from CRA on Article XXI of the Canada-US Tax Treaty 9900795

1996 Newsletter from CRA on Article XXI of the Canada-US Tax Treaty

1991 Letter from CRA on Article XXI of the Canada-US Tax Treaty

1989 Letter from CRA on Article XXI of the Canada-US Tax Treaty 5-8223