Multi-reference annotations are annotations pointing to more than one reference, consisting of a dimension and associated tag. 
   Namespace:   Autodesk.Revit.DB  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
  Since:  2014 
Syntax
Remarks
 Multi-reference annotations can be used to label and dimension Rebar elements, and are labeled in the user interface as "Multi-rebar annotations". MultiReferenceAnnotation is the annotation object instance. This class includes a reference to the associated dimension and tag element.