Used namespace:
<tabs>
<tab name="UWP">
<source lang = "xml">
xmlns:cv="using:UBIK.WinX.UI.CollectionView"
</source>
</tab>
<tab name="Xamarin">
<source lang = "xml">
xmlns:controls="clr-namespace:UBIK.CPL.Controls;assembly=UBIK.CPL"
</source>
</tab>
</tabs>