Added (r:ProjectReferenceEventArgs)

Avoiding 
/fsharpbinding/monodevelop/MonoDevelop.FSharpBinding/FSharpLanguageBinding.fs(84,89): error FS0072: Lookup on object of indeterminate type based on information prior to this program point. A type annotation may be needed prior to this program point to constrain the type of the object. This may allow the lookup to be resolved. 

on (84,89) and (85,93)