The tax treaty has been signed between Canada and the Republic of Serbia. Finance Canada mentions that the withholding rate for dividends for associated companies will be 5% and 15% in all other cases.
One interesting note in the treaty is that residence for “other than an individual” (i.e. a corporation) will be decided by the competent authorities looking at effective management and control as well as incorporation place and other relevant criteria. And, if the competent authorities have not made a decision, no treaty benefits will be given.
You can find a copy of the announcement and tax treaty here.