anchor.diff:      
       member this.AddReferences(libs) = this.AddReferences(libs, NuspecReferences.All)
       
  -    member this.AddFrameworkAssemblyReference(framework : FrameworkIdentifier, assemblyName) : InstallModel = 
  +    member this.AddFrameworkAssemblyReference(reference) : InstallModel = 
           this.AddOrReplaceGroup(
  -            framework.Group,
  +            reference.TargetFramework.Group,
               (fun group ->
                   group.ReplaceFramework(
  -                    framework,
  -                    (fun _ -> InstallFiles.empty.AddFrameworkAssemblyReference assemblyName),
  -                    (fun files -> files.AddFrameworkAssemblyReference assemblyName))),
  +                    reference.TargetFramework,
  +                    (fun _ -> InstallFiles.empty.AddFrameworkAssemblyReference reference.AssemblyName),
  +                    (fun files -> files.AddFrameworkAssemblyReference reference.AssemblyName))),
               (fun _ -> None))
       
       member this.AddFrameworkAssemblyReferences(references) : InstallModel = 
           references 
  -        |> Seq.fold 
  -               (fun model reference -> model.AddFrameworkAssemblyReference(reference.TargetFramework, reference.AssemblyName))
  -                this
  +        |> Seq.fold (fun model reference -> model.AddFrameworkAssemblyReference reference) this
       
       member this.FilterBlackList() = 
           let blackList = 
  
positive.code:     
      
      member this.UseLowerVersionLibIfEmpty() =
          let group = 
              FrameworkVersion.KnownDotNetFrameworks
              |> List.rev
              |> List.fold (fun (group : FrameworkGroup) lowerVersion -> 
                  let newFiles = group.GetReferences(DotNetFramework(lowerVersion))
                  if Set.isEmpty newFiles then group  else 
                  FrameworkVersion.KnownDotNetFrameworks
                  |> List.filter (fun version -> version > lowerVersion)
                  |> List.fold (fun (group : FrameworkGroup) upperVersion -> 
                          let framework = DotNetFramework(upperVersion)
                          match Map.tryFind framework group.Frameworks with
                          | Some files when Set.isEmpty files.References -> 
                              { group with Frameworks = 
                                              Map.add framework { References = newFiles
                                                                  ContentFiles = Set.empty } group.Frameworks }
                          | _ -> group) group) (Map.find FrameworkIdentifier.DefaultGroup this.Groups)
  
          { this with Groups = Map.add FrameworkIdentifier.DefaultGroup group this.Groups }
      
      member this.UseLowerVersionLibForSpecicalFrameworksIfEmpty() = 
          let newFiles = this.GetReferences(DotNetFramework(FrameworkVersion.V4_5))
  
negative.code:           PackageVersion = packageVersion
            DefaultFallback = InstallFiles.empty
            Groups = Map.add FrameworkIdentifier.DefaultGroup group Map.empty }
     
      member this.GetFrameworks() = 
          this.Groups
          |> Seq.map (fun kv -> kv.Value.Frameworks)
  