References

All the external references for a project can be seen under the References node
If you cannot see the References node then you need to "show all files" for that project.
SS
You can write code against external components by adding references to your project.
To remove a reference right click on that particular reference and select Remove

Types of References

File References
Project References

When you choose Add Reference you will see the Reference Manager dialog box.
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.NET tab	.NET Framework class libraries and assemblies
COM tab	COM components
Project tab	Project to Project class libraries and assemblies. These are references to projects that contain assemblies. This will create a dependency when the project is built
Browse tab	This is for individual file references. This can be used to add references that were in the GAC and are then copied locally to be included into a Setup project.
Recent tab

Adding References

To add a reference right click and select Add a Reference
VSTO projects behave slightly differently to regular class libraries and for that reason will not appear in this list.
To add a reference to a VSTO project you need to choose the Browse tab and select the most recent version of that dll in the bin folder.

VB.NET

The References node is not displayed by default in the Solution Explorer
This can be seen by clicking on the 'Show All Files' icon at the top
These references are also displayed on a tab on the Properties dialog box