4/5 XText DSL further grammar constructs

[brixomatic]

First of all: great tutorial, thanks a lot! Unfortunately I'm stuck with the "sequel of" part: Although I defined the isbn as "ID", the auto completion won't suggest any isbn number (it suggest "sequel of", so compiling had worked). If I enter an isbn-number by copying one the editor tells me: "couldn't resolve reference to Book J1235". Any suggestions what might have gone wrong? I'm using Xtext 2.1 by the way.