Goldmann, W. M., Ahola, J., Mankinen, O., Kantola, A. M., Komulainen, S., Telkki, V.-V. “Determination of Phenolic Hydroxyl Groups in Technical Lignins by Ionization Difference Ultraviolet Spectrophotometry (∆ε-IDUS method)”, Periodica Polytechnica Chemical Engineering, 61(2), pp. 93–101, 2017. https://doi.org/10.3311/PPch.9269