Prof. Helmut Wagner published his paper “Structural change, rebalancing, and the danger of a middle-income trap in China” in the BOFIT Policy Brief series (BOFIT Policy Brief 2018 No. 6). He presented a first version of this paper early this year, when he attended an ECB-Conference in Helsiniki, Finland as the Keynote-Speaker. You can find the paper and an abstract here.
The paper is also available as CEAMeS Discussion Paper No. 13 (you can find it here).