Furthermore, I did notice that in the IP 8 Spouse or Common law partner in Canada class manual, you can find form IMM5409 under the forms needed (page 12) and also on section 10.1 you can find on the common law section a "a statutory declaration of the common law relationshio (included in the package" (page 44).
now i am more confused. please check the link below for reference.
http://www.cic.gc.ca/englisH/resources/manuals/ip/ip08-eng.pdf