1. Functions of natural organic matter in changing environment;E de Albuquerque Brocchi,2013
2. Humic substances II. In search of structure;GJ Lawson,1989
3. Nitrohumic acids from Victorian brown coal;AF Patti;Sci Total Environ,1992
4. Extraction and chemical characteristics of nitro-humic acids from coals and composts;AM Syahren;J Trop Agric and Fd Sc,2008
5. Chemistry of coal utilization;HC Howard,1945