“…They appear in the classification of countable 2‐homogeneous trees from [
5], and have since been important in the theory of permutation groups; cf., e.g., [
1, 3, 4]. More recently, they were shown to be dp‐minimal in [
17], and the automorphism group of the unique countable one was studied in [
10], while the interest in similar structures goes back at the very least to [
14, 20], where they were used as a base to produce examples in the context of Ehrenfeucht theories. Here we study
, and some of the expansions defined in [
7], from the viewpoint of domination, in the sense of [
13].…”