Retrieve count of Linked Requirements via API

Hi,

I am looking to use the API to retrieve 

1) Total number of requirements associated with a Project

2) How many of those are actually linked with Test cases

I believe, I can get (1) by calling GET on:

projects/ProjectId/requirements

Not sure how to get Linked requirements though.

There is a section of API that talks about Linked Items but not sure, if that is what I need to explore.

Can someone point to the API calls that would be needed to be made?

Thanks in advance.

Regards

NSB