How to use a User control from another application

I need to include two user controls(header and footer) from another application into my application. The user controls were register in the web.config
<pages>
<controls>
    <add tagPrefix="rainbowheader" src="include/DesktopPortalBanner.ascx" tagName="header"/>
    <add tagPrefix="rainbowfooter" src="include/DesktopPortalFooter.ascx" tagName="footer"/>
</controls>
</pages>
but getting this error: The relative virtual path '../include/DesktopPortalBanner.ascx' is not allowed here

Any idea?

 
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