RQM Rest API get linked requirements

Hello,

I'm using RTC 3 and when I extract the testcases requirements are not shown in the xml file even if in RQM there are test cases with linked requirements from RRC.
I use the following url for extraction:
https://server:9443/qm/service/com.ibm.rqm.integration.service.IIntegrationService/resources/project/testcase

In https://jazz.net/wiki/bin/view/Main/RqmApi I see that test case should have a requirement node but this is missing in my xml file.

Any ideas what should I do ?

Thanks.