Khalil, K. et al. 2010. Chitosan as an eco-friendly heterogeneous catalyst for Michael type addition reactions. A simple and efficient route to pyridones and phthalazines. European Journal of Chemistry. 1, 4 (Dec. 2010), 252–258. DOI:https://doi.org/10.5155/eurjchem.1.4.252-258.211.