I. Barmina, M. Zake, R. Valdmanis, A. Arshanitsa, V. Solodovnik, G. Telysheva, The Effect of Birch-Bark Addition on the Elemental Composition and Combustion Characteristics of Different Types of Biomass Pellets, Chemical Engineering Transactions. 39 (2014) 1525-1530. doi:10.3303/CET1439255.