New Post: Using Biztalk Deployment Framework with multiple BizTalk Applications

I have just seen this post and I am wondering how would you reference BizTalk Application3 from BizTalk Application 2, in case of application reference scenarios. Do we need to add anything on the global  Deployment.btdfproj to make it work? We have a similar situation. We are using the global  Deployment.btdfproj and two more .btdfproj files for two BizTalk applications. Our BizTalk application 1 is referencing BizTalk application 2. We are using the below XML segment on the application 1 of Deployment.btdfproj file. However, it seems that the Deployment.btdfproj of applicaiton1 is not recognizing the reference of "BizTalkApplication2".