Mun, Ji Sun, et al. “Characterization of Kraft Lignin Prepared from Mixed Hardwoods by 2D HMQC and 31P NMR Analyses”. BioResources, vol. 17, no. 4, Nov. 2022, pp. 6626-37, https://ojs.bioresources.com/index.php/BRJ/article/view/22110.