[isabelle] Multiple equivalences

What is the right way to formulate in Isabelle a theorem which states that every two of 10 logical expressions are equivalent?
This is equivalent to 9 equivalences:
(1) <-> (2)
(1) <-> (10)
but that seems not the best way to formulate it.
What is the right way?
(The same for 10 equal (not necessarily logical) terms?)
Victor Porton - http://portonvictor.org

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