An upper bound for a Hilbert polynomial on quaternionic Kahler manifolds
  In this article we prove an upper bound for a Hilbert polynomial on quaternionic Kaehler manifolds of positive scalar curvature. As corollaries we obtain bounds on the quaternionic volume and the degree of the associated twistor space. Moreover the article contains some details on differential equations of finite type. Part of it is used in the proof of the main theorem. 
Uwe Semmelmann, Gregor Weingart