On the multiplicity function of ergodic group extensions of rotations
G. Goodson, J. Kwiatkowski, M. Lemańczyk, P. Liardet (1992)
Studia Mathematica
Similarity:
For an arbitrary set A ⊆ ℕ satisfying 1 ∈ A and lcm(m₁,m₂) ∈ A whenever m₁,m₂ ∈ A, an ergodic abelian group extension of a rotation for which the range of the multiplicity function equals A is constructed.