ohio - state.edu/Professional/OSU/Faculty/jstjohn/Common%20rocks/Peat.htm http://www.chemical-engineering.co/2011/06/27/bituminous-coal/ http://en.wikipedia.org/wiki/Anthracite http://museumvictoria.com.au/melbournemuseum/discoverycentre/600-million-years/timeline/tertiary/brown-coal/ http://www.physic.ut.ee/materjalimaailm/Kirjed/Fossiilkutused.htm Kivisüsi • 27% maailma primaarenergiast annab süsi.
annaabi.ee 
