A. Beylich and U. Graefe, “Investigations of annelids at soil monitoring sites in Northern Germany: reference ranges and time-series data”, Soil Org, vol. 81, no. 2, pp. 175–196, Aug. 2009, Accessed: Apr. 06, 2025. [Online]. Available: https://soil-organisms.org/index.php/SO/article/view/195