1. The council of the European communities , Council directive of 12 June 1986 on the protection of the environment, and in particular of the soil, when sewage sludge is used in agriculture , 1986
2. The presence of contaminations in sewage sludge – The current situation
3. European Commission, Sewage sludge production and disposal, accessed March 22, 2019, https://ec.europa.eu/eurostat/web/products-datasets/product?code=env_ww_spd
4. Benefits and risks of long-term recycling of pharmaceutical sewage sludge on agricultural soil