Classification
CXA - Coal and fossil fuel - chemistry and technology
1
CXR - Natural gas and petroleum - chemistry and technology
1
CXRU - Synthetic fuels
EBA - Energy production, energy technology
1
ECA - Energy resources
1
EEA - Coal - general
1
EHA - Renewable energy sources
1
ENA - Energy from biomass and waste
1
UKE - Environment and energy resources
1