[plt-scheme] @tech in other manuals

How can I create a @tech reference to a term that was @deftech'ed in 
another manual? I can't figure out how to create a reference to 
@tech{prefab} from (lib "scribblings/guide/guide.scrbl").

For now I've just created a link to that section of the guide, but it 
seems like it would be more appropriate to use @tech.

Thanks,
Dave