VaitkutėD., BaltrėnaitėE., BoothC. A., and FullenM. A. “Does Sewage Sludge Amendment to Soil Enhance the Development of Silver Birch and Scots Pine?”. Hungarian Geographical Bulletin, Vol. 59, no. 4, Dec. 2010, pp. 393-10, https://ojs.mtak.hu/index.php/hungeobull/article/view/3118.