anchor.diff:              self.getYTop() = r.getYTop() &&
               self.getYBottom() = r.getYBottom()
   
  +    type ReferenceType =
  +    | ReferenceAddress  = 0
  +    | ReferenceRange    = 1
  +    | ReferenceFunction = 2
  +    | ReferenceConstant = 3
  +    | ReferenceString   = 4
  +    | ReferenceNamed    = 5
  +
  +    [<AbstractClass>]
       type Reference(path: string option, wbname: string option, wsname: string option) =
           let mutable _path: string option = path
           let mutable _wbn: string option = wbname
  
positive.code: 
      and ReferenceNamed(wsname: string option, varname: string) =
          inherit Reference(None, None, wsname)
          member self.Name = varname
          override self.ToString() =
              match self.WorksheetName with
  
negative.code:         abstract member Resolve: string -> Workbook -> Worksheet -> unit
          abstract member WorkbookName: string option with get, set
          abstract member WorksheetName: string option with get, set
          abstract member Type: ReferenceType
          default self.Path
              with get() = _path
              and set(value) = _path <- value
  