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Makkar, Harinder P. S.. (2003). Quantification of Tannins in Tree and Shrub Foliage || Measurement of Total Phenolics and Tannins Using Folin-Ciocalteu Method. , 10.1007/978-94-017-0273-7(Chapter 3), 49–51. doi:10.1007/978-94-017-0273-7_3 
An interview with Sci-Hub Founder Alexandra Elbakyan,Who exactly should pay for academic research