instructions for adding venues?

I haven't been adding venues for some time. There are these new link fields. Where can I find some information about them and magicnumbers etc? I tried to look form WikiThing, but found only general information.

The feature Get this book is connected to LibraryThing Local information, isn't it? In what form the link to the library catalogue has to be added so that the search from Get this book works?

I found some info about this in topic:

New features: More URL options for venues

Maybe I get this by looking how things are done with other libraries. I think I understand now how to make things work (or at least ISBN search) for Voyager libraries.

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Edited to add a quotation mark.