калций
68ПРОМИШЛЕНОСТ- MT
6816металургия - BT1 цветен метал
- BT2 метали
Mapping
- EXM agrovoc: Agrovoc (FAO - Food and Agriculture Organization)
- EXM gemet: GEMET (GEneral Multilingual Environmental Thesaurus - EEA)
- EXM unesco: UNESCO (United Nations Educational, Scientific and Cultural Organization)
Bulgarian)