I can never remember the URI format for resources embedded in assemblies. So:
assembly://<assemblyname>/<namespace>/<resource>
The <namespace> part can include folder names separated from the base assembly namespace by dots (.). For example a Spring configuration file located in a SpringConfig folder for an application with a default namespace of Mail.Merge.Console would have a resource definition of:
assembly://Mail.Merge.Console/Mail.Merge.Console.SpringConfig/SpringDataAccess.xml