id	keyword
asir-41930	buses
asir-41930	electric
asir-41930	emission
asir-41930	cost
asir-41930	diesel
asir-41930	carbon
asir-41930	diesel buses
asir-41930	sendai
asir-41930	total
asir-41930	system
asir-41930	research
asir-41930	model
asir-41930	electricity
asir-41930	number
asir-41930	bus system