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Conjecture Does there exist graphs
and
from Class 1 such that there Cartesian product is from Class 2?
and
from Class 1 such that there Cartesian product is from Class 2? It is known that there are graphs
and
which are from Class 2 and their product is from Class 1. Our problem asks the symmetric question. Let us also note that from the classical result of A. Kotzig we imply that there are no regular graphs
and
satisfying the conjecture.
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