xr-hyper – Inter-document hyper-references

The pack­age de­scribes it­self as a de­vel­op­ment ver­sion of the stan­dard pack­age xr; it can cre­ate hy­per­links to the ex­ter­nal doc­u­ments that are cross-ref­er­enced.
It is avail­able as part of the hy­per­ref dis­tri­bu­tion; hy­per­ref it­self was long ago mod­i­fied to work with this pack­age.