sentences: forming fossil fuels requires deposition and burial of decaying vegetation
docs: pigmentation is deposition. chemical_vapor_deposition is thin_film_deposition. fossil is remains. decay is natural_process. physical_vapor_deposition is microfabrication. fossil_fuel_generation is geologic_process. decomposition is decay. physical_vapor_deposition is thin_film_vacuum_deposition. fossil is petrification_of_living_being.