Skute, A. et al. 2015. Determining the Isotopic Composition of Nitrate in the River Daugava and Loads of Nitrogen to the Gulf of Riga. ENVIRONMENT. TECHNOLOGIES. RESOURCES. Proceedings of the International Scientific and Practical Conference. 2, (Jun. 2015), 280–283. DOI:https://doi.org/10.17770/etr2015vol2.249.