Nuget package subfolder

I want to create a nuget package with referenced dll to be copied into subfolders . How to specify the output path in nuspec file.

<package xmlns="http://schemas.microsoft.com/packaging/2010/07/nuspec.xsd"><metadata><id>Nuget1</id><version>1.x.xx</version><title></title><authors></authors><owners></owners><requireLicenseAcceptance>false</requireLicenseAcceptance><projectUrl></projectUrl><description></summary><language>en-US</language></metadata><files> <file src="..\.dll" target="lib\net472\sample.dll" /></files><Project>

In this nuspec i want to copy the sample.dll to subfolder in output directory.If I specify the subfolder after net472\sub\sample.dll then it wont add the dll as reference at all.