diff --git a/Assets/MackySoft/MackySoft.SerializeReferenceExtensions/Samples~/GetStarted/Scripts/Runtime/MackySoft.SerializeReferenceExtensions.Example.GetStarted.asmdef b/Assets/MackySoft/MackySoft.SerializeReferenceExtensions/Samples~/GetStarted/Scripts/Runtime/MackySoft.SerializeReferenceExtensions.Example.GetStarted.asmdef
index 24bdbe0..3e96a73 100644
--- a/Assets/MackySoft/MackySoft.SerializeReferenceExtensions/Samples~/GetStarted/Scripts/Runtime/MackySoft.SerializeReferenceExtensions.Example.GetStarted.asmdef
+++ b/Assets/MackySoft/MackySoft.SerializeReferenceExtensions/Samples~/GetStarted/Scripts/Runtime/MackySoft.SerializeReferenceExtensions.Example.GetStarted.asmdef
@@ -10,7 +10,9 @@
     "overrideReferences": false,
     "precompiledReferences": [],
     "autoReferenced": true,
-    "defineConstraints": [],
+    "defineConstraints": [
+        "UNITY_2019_3_OR_NEWER"
+    ],
     "versionDefines": [],
     "noEngineReferences": false
 }
\ No newline at end of file
diff --git a/MackySoft.SerializeReferenceExtensions.Example.GetStarted.csproj b/MackySoft.SerializeReferenceExtensions.Example.GetStarted.csproj
index be7a2b7..5fdd382 100644
--- a/MackySoft.SerializeReferenceExtensions.Example.GetStarted.csproj
+++ b/MackySoft.SerializeReferenceExtensions.Example.GetStarted.csproj
@@ -281,33 +281,6 @@
     <Reference Include="UnityEditor.UnityConnectModule">
       <HintPath>C:\Program Files\Unity\Hub\Editor\2020.3.24f1\Editor\Data\Managed\UnityEngine\UnityEditor.UnityConnectModule.dll</HintPath>
     </Reference>
-    <Reference Include="UnityEditor.Graphs">
-      <HintPath>C:\Program Files\Unity\Hub\Editor\2020.3.24f1\Editor\Data\Managed\UnityEditor.Graphs.dll</HintPath>
-    </Reference>
-    <Reference Include="UnityEditor.Android.Extensions">
-      <HintPath>C:\Program Files\Unity\Hub\Editor\2020.3.24f1\Editor\Data\PlaybackEngines\AndroidPlayer\UnityEditor.Android.Extensions.dll</HintPath>
-    </Reference>
-    <Reference Include="UnityEditor.iOS.Extensions">
-      <HintPath>C:\Program Files\Unity\Hub\Editor\2020.3.24f1\Editor\Data\PlaybackEngines\iOSSupport\UnityEditor.iOS.Extensions.dll</HintPath>
-    </Reference>
-    <Reference Include="UnityEditor.WindowsStandalone.Extensions">
-      <HintPath>C:\Program Files\Unity\Hub\Editor\2020.3.24f1\Editor\Data\PlaybackEngines\WindowsStandaloneSupport\UnityEditor.WindowsStandalone.Extensions.dll</HintPath>
-    </Reference>
-    <Reference Include="SyntaxTree.VisualStudio.Unity.Bridge">
-      <HintPath>C:\Program Files (x86)\Microsoft Visual Studio Tools for Unity\16.0\Editor\SyntaxTree.VisualStudio.Unity.Bridge.dll</HintPath>
-    </Reference>
-    <Reference Include="Unity.Plastic.Newtonsoft.Json">
-      <HintPath>Library\PackageCache\com.unity.collab-proxy@1.15.4\Lib\Editor\PlasticSCM\Unity.Plastic.Newtonsoft.Json.dll</HintPath>
-    </Reference>
-    <Reference Include="Unity.Plastic.Antlr3.Runtime">
-      <HintPath>Library\PackageCache\com.unity.collab-proxy@1.15.4\Lib\Editor\PlasticSCM\Unity.Plastic.Antlr3.Runtime.dll</HintPath>
-    </Reference>
-    <Reference Include="unityplastic">
-      <HintPath>Library\PackageCache\com.unity.collab-proxy@1.15.4\Lib\Editor\PlasticSCM\unityplastic.dll</HintPath>
-    </Reference>
-    <Reference Include="log4netPlastic">
-      <HintPath>Library\PackageCache\com.unity.collab-proxy@1.15.4\Lib\Editor\PlasticSCM\log4netPlastic.dll</HintPath>
-    </Reference>
     <Reference Include="Newtonsoft.Json">
       <HintPath>Library\PackageCache\com.unity.nuget.newtonsoft-json@2.0.0\Runtime\Newtonsoft.Json.dll</HintPath>
     </Reference>