References
- Bill of energy efficiency. (2011). EU, Brussels, Maszynopis.
- Borek, K., Barwicki, J., Majchrzak, M., Mazur, K., Wardal, W. (2015). Evaluation of the impact of digestate formed during biogas production on the content of heavy metals in soil. Agricultural Engineering, No 2, 15-23
- New developments in Lawrence Berkeley National Laboratory. (2013). USA.
- Information of Sustainable Energy Financial Facility. (2013). Warsaw.
- Information of the National Fund for Environment Protection and Water Management. (2012). Warsaw, Poland.
- Resolution of the Council of Ministers No. 202/2009 on the Polish Energy Policy until 2030, Brussels, Belgium.
- Solar collector market in Poland 2010. Institute for Renewable Energy, Warsaw, Poland
- Solar thermal markets in Europe. Trends and market statistics 2010, European Solar Thermal Industry Federation
- MIT new developments on energy projects – University information. (2013). New York, USA.
- Renewable energy sources in 2010. Central Statistical Office of Poland (GUS)
- Research activity in Oregon State University. (2013). Oregon, USA.
- Solar Botanic developments on renewable technologies. (2013). London.
- University of Texas research activity information. (2012). Texas, USA.
- Interreg EU - Baltic Sea Region - Baltic Slurry Acidification Project 2016-2019
- Project agreement BIOSTRATEG1/269056/5/NCBR/2015 z dnia 11.08.2015
- Wardal, W.J. et al., (2015). Technical and economical aspects of biogas production from agricultural sources including Polish conditions. Agricultural Engineering, No. 2(154), 137-148.