“…Their choice is based on the asymptotic behavior of solutions at infinity. In particular, for elliptic boundary value problems in exterior domains and domains with cylindrical or conical outlets to infinity, ABCs in differential form were systematically developed during the last decades (see e.g., [1,2,4,5,7,9,10,14,23,24,32,34]) and the papers quoted there.) The common feature of local ABCs are estimates for the truncation error of the form u ∞ − u R = O(R −γ ) as R tends to infinity, with some γ > 0.…”