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Unity Error CS0246 Please, Help me

Hello everyone.

 I received a message in console box in Unity ( My Unity version 2017.3.0f3 Personal )

"Assets/Vuforia/Scripts/BackgroundPlaneBehaviour.cs(19,45): error CS0246: The type or namespace name `BackgroundPlaneAbstractBehaviour' could not be found. Are you missing an assembly reference?"

And

"Assets/Vuforia/Scripts/CloudRecoBehaviour.cs(18,39): error CS0246: The type or namespace name `CloudRecoAbstractBehaviour' could not be found. Are you missing an assembly reference?"

 

I search how to solve this problem and follow to do it. but unsuccessful.

I don't know how to solve it. please help me.

I attached a pic to this topic.Image removed.

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