Classification
EFK - Petroleum deposits, natural gas deposits
10
EFE - Petroleum geology
2
EFN - Petroleum exploration, natural gas exploration
2
EFP - Petroleum production, natural gas production
2
EWA - Energy economy
2
GBAK - Paleontology
1
GCAA - Regional geology - Germany
1
GHA - Petrology - general
1
GMAD - Organic geochemistry
1