Query RQM for plan items associated with test case via REST

I am trying to get the list of plan items (RTC workitems) associated with a test case using the REST API. Looking at the XML returned for https://.../jazz/secure/service/com.ibm.rqm.integration.service.IIntegrationService/resources/<project>/testcase/urn:com.ibm.rqm:testcase:7817 I don't see this information.

The RQM API docs suggest there should be a <workitem> element in RQM 2.0 which is handled differently in later releases, but I haven't had much luck figuring out what the RTC schema looks like or how to query it unless I happen to have a specific URL from RQM.

RQM is at 2.0.1.1 iFix 2
RTC is at 2.0.0.2 iFix 6

John