Pessi, Yrjö, Mikko Ylänen, Auvo Leskelä, and Jorma Syvälahti. “Autumn and Winter Application of Nitrogen Fertilizers on Clay Soils”. Agricultural and Food Science 43, no. 2 (May 1, 1971): 76–85. Accessed April 12, 2025. https://journal.fi/afs/article/view/71786.