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windows phone 8 build

i have unity 4.2 free version and vuforia vuforia-unity-android-ios-2-6-7

when i build project for windows phone 8 it give me error

 

Assets/Qualcomm Augmented Reality/Scripts/Internal/WebCamTexAdaptorImpl.cs(17,13): error CS0246: The type or namespace name `WebCamTexture' could not be found. Are you missing a using directive or an assembly reference?  why? please help for build. thanks