 This idea was further developed by Brian Loar (1981: ch. 4), Jackson, Pargetter and Prior (1982), and Michael Esfeld and Christian Sachse (Sachse 2007; Esfeld and Sachse 2007). Esfeld and Sachse (2007) and Sachse (2007) describe how this insight can be accommodated within the high-level science by constructing fine-grained versions of the high-level types—so called ‘functional sub-types’—which can then be linked to the relevant low-level kinds, using the resources of high-level science.