Resources need to be delete in APO

Dear all,

I want to delete resource in APO and know that it can be deleted when there are no any dependecies information relevant to resource such as planned order, PDS, Supply Chain Model. I have deleted all except one, that is supply chain model as picture below

But it seems I have not assign this resource to this model, when I tried to delete all resources which have been assigned to this model but SAP said that no any object there

Please help to explain me what are happenning behind? Thanks all

Regards,

Vu Pham