Invitation Letter of Duly Authorized Tourism Unit

Hi. I live in the UAE, and I'm from Syria, and on March 21st, I'm supposed to be going to China for a school tourism trip. When I went to the Chinese Embassy last week, they told me that i needed not only a regular invitation letter from the host company, but an Invitation Letter of Duly Authorized Tourism Unit. I'm not quite sure what this means, and how it could be obtained. Is there any way you can assist? Thank you