| (subclass FossilFuel Fuel) | Mid-level-ontology.kif 1687-1687 | Fossil fuel is a subclass of fuel |
| (subclass FossilFuel PetroleumProduct) | Mid-level-ontology.kif 1688-1688 | Fossil fuel is a subclass of petroleum product |
| (subclass LiquefiedPetroleumGas FossilFuel) | Mid-level-ontology.kif 1705-1705 | Liquefied petroleum gas is a subclass of fossil fuel |
| (subclass Gasoline FossilFuel) | Mid-level-ontology.kif 1709-1709 | Gasoline is a subclass of fossil fuel |
| (subclass DieselFuel FossilFuel) | Mid-level-ontology.kif 1714-1714 | Diesel fuel is a subclass of fossil fuel |
| (subclass Coal FossilFuel) | Geography.kif 2018-2018 | Coal is a subclass of fossil fuel |
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