Within the last 4 years if you spent 183 days or more in a country other than Canada then you must provide a Police Clearance Certificate (PCC) from that country. If you cannot get the PCC then in the explain section explain why you cannot get the PCC. If you have the PCC, then I think it is okay to just write a sentence saying "The PCC from so and so country has been attached" in the explanation section. That is what I did. Hope this helps. Thanks.