(done) Question about different ISBN

[Olga]

I'm librarian. I'm sorting old classic books (russian).
There are 4 same editions with different ISBN. I checked with the publisher, it's really identical editions (cover, data, format - all identical). They publish this book every two years with different ISBN.
There are 0 shelvings (only first edition has).
I would like to merge them, but it is wrong, yes? Only combine?
It's old book, there are dozens of editions.

[Renske]

You should only combine them. A different ISBN makes it a valid edition even if all other details are the same.

[Olga]

Renske wrote: "You should only combine them. A different ISBN makes it a valid edition even if all other details are the same."

Ok, thanks.