hello all, my in laws from China were here visiting last summer for 3 months (June - Sept). They want to come visit again this April for another 3 to 4 months. Do I have to do up another invitation letter to them? They already have an entry visa to Canada on their Chinese passport. I think it's good for 10 years. Is there anything else they need to do on their end? Is there anything else I need to do here? Thank you!