three errors

/media/home2/vivienne/Urho3D-Hangars/Source/HangarsClient/HangarsClientApplication.cpp|58|error: undefined reference to 'RemoteGameLogic::RemoteGameLogic(Urho3D::Context*)'|
/media/home2/vivienne/Urho3D-Hangars/Source/HangarsClient/HangarsClientApplication.cpp|68|error: undefined reference to 'MainMenuView::MainMenuView(Urho3D::Context*, Urho3D::Renderer*)'|
/media/home2/vivienne/Urho3D-Hangars/Source/EngineStd/EngineApplication.cpp|56|error: undefined reference to 'Urho3D::Script::Script(Urho3D::Context*)'|
||=== Build finished: 3 errors, 0 warnings ===|