Dubrovskis, Vilis, Imants Plūme, Andis Spīdāns, and Indulis Straume. 2007. “FACILITY OF BIOGAS PRODUCTION IN LATVIA”. ENVIRONMENT. TECHNOLOGIES. RESOURCES. Proceedings of the International Scientific and Practical Conference 1 (June): 46-51. https://doi.org/10.17770/etr2007vol1.1717.