Created Unassigned: NPOI.HSSF.dll file missing [13220]

Hi,

I was wondering if someone from here could make me aware of how I can restore
a missing NPOI.HSSF.dll file in the bin folder of my project solutions.

If I need to download a new copy of it, that's fine, but I have no clue where to find it
or how to install it successfully.

I attempted to publish a web application not too long ago. And I received the following
error:

"Copying file bin\NPOI.HSSF.dll to obj\Release\AspnetCompileMerge\Source\bin\NPOI.HSSF.dll failed. Could not find file 'bin\NPOI.HSSF.dll'.

Any help with this would be greatly appreciated.
Thanks!