Facebook.Unity.Editor/UnityReferences/5.xml

  <ItemGroup>
    <Reference Include="UnityEditor">
      <HintPath>$(UNITY_MANAGED_DIR)UnityEditor.dll</HintPath>
    </Reference>
    <Reference Include="UnityEngine">
      <HintPath>$(UNITY_MANAGED_DIR)UnityEngine.dll</HintPath>
    </Reference>
  </ItemGroup>