How to Get the list of attached observers on a document?

I have attached a Observer on a document as below:

 {            InterfacePtr<IActiveContext> iActiveContext(GetExecutionContextSession()->GetActiveContext(), UseDefaultIID());            if(iActiveContext == nil)                break;            else            {                IDocument *idocument= iActiveContext->GetContextDocument();                if(idocument == nil)                    break;                UIDRef docRef(::GetUIDRef(reinterpret_cast<IPMUnknown*>(idocument)));                InterfacePtr<IObserver> docObserver(docRef, IID_ICSDTSELECTIONOBSERVER);          if (docObserver != nil)                {                    docObserver->AutoAttach();                }
}


 }}           } //else}        }