“…So we need to identify which iterative roots are genetic or not. This problem was considered in [11] for a special class of PM functions of height 1, each of which has a characteristic interval bounded by an endpoint of the domain and is homeomorphic onto the characteristic interval but does not reach an endpoint of the characteristic interval outside. Theorem 2 of [12] indicates that all its iterative roots are in the simplest mode of 1-extension.…”