(subclass Fuel Substance) | Mid-level-ontology.kif 1693-1693 | Fuel is a subclass of substance |
(subclass FossilFuel Fuel) | Mid-level-ontology.kif 1687-1687 | Fossil fuel is a subclass of fuel |
(subclass Charcoal Fuel) | Cars.kif 1670-1670 | Charcoal is a subclass of fuel |