Debongnie, Ph., & Mestdagh, M. (1987). An Electron-paramagnetic-res and Potentiometric Study of the Complexation of Copper Ions By Galacturonic Acid and Galacturonans. Carbohydrate Research, 170(2), 137-149. https://doi.org/10.1016/S0008-6215(00)90900-5 (Original work published 1987)