Before revision:  We complement the latter result by showing that, for any fixed p\geq 3 the problem becomes NP-complete when restricted to split (S_3,\ldots,S_p)-free graphs, where S_q denotes the q-sun graph.
After revision:  We complement the polynomial-time solvability results for split strongly chordal graphs by showing that, for any fixed p\geq 3 the problem becomes NP-complete when restricted to split (S_3,\ldots,S_p)-free graphs, where S_q denotes the q-sun graph.