Gałka, A. and Szmeja, J. 2013. Distribution, abundance and environmental conditions of the clonal aquatic fern Salvinia natans (L.) All. in the Vistula delta (Baltic Sea Region). Biodiversity: Research and Conservation. 28, (Feb. 2013), 45–53. DOI:https://doi.org/10.2478/v10119-012-0020-7.