When you open a document using iTWO cx Mobile the right most tab is the Related tab.
This tab shows you all the documents associated with the document you have opened.
On iTWO cx this is shown under Linked.
Only documents you have access to in the Linked section will be shown on the related Tab.
Only Correspondence documents and Publication Space Documents are displayed in the Related tab.
For eg: Transmittal, Contract Administration documents are not shown on this tab.