“…Fortunately, the number of research papers that do not provide a test of the proposed model also remains limited to a few cases. [78,85,115,118] It is remarkable that many researchers claim that they present a generic model that can be applied to many different settings, while each researcher comes up with a completely different approach. We found that [15,42,44,56,57,72,78,85,92,93,100,109,115,116,117, 118] present a more or less generic approach to incorporate skills in workforce planning problems.…”