Finding semantic references of a dimension

Hi all,

I'm trying to figure out how to access the semantic references of a dimension using Toolkit.
For a 3D annotation that is created by 'show dimensions' and is as such derived from a driving dimension this can be done by using the sequence
ProAnnotationElementGet
ProAnnotationelemIsIncomplete (to figure out whether semantic references were assigned)

For a 3D annotation that is created as a driven dimension this does not work. I tried ProDimensionAdditionalRefsGet but the return value is PRO_TK_BAD_INPUTS although type=PRO_DIMENSION

Can anyone point me in the right direction to check and get access to the assigned semantic references?