Lazdiņa, D., A. Lazdiņš, Z. Kariņš, and V. Kāposts. “Effect of Sewage Sludge Fertilization in Short‐rotation Willow Plantations”. Journal of Environmental Engineering and Landscape Management, Vol. 15, no. 2, June 2007, pp. 105-11, doi:10.3846/16486897.2007.9636916.