Unable to add a reference to project '{0}'. Portable Library projects can only reference other Portable Library projects and assemblies.
Unable to add a reference to project '{0}'. The current project's target is not one of or compatible with the targets of Portable Library project '{0}'.
Unable to add a reference to project '{0}'. The targets of Portable Library project '{0}' are not the same or compatible with the targets of the current Portable Library project.
YUnable to add a reference to project '{0}'. The current project does not support references to Portable Library projects.