Comparative study for differentiation of aquatic humic-type organic constituents by capillary zone electrophoresis using polyvinyl alcohol-coated capillaryPeuravuori, Juhani; Lehtonen, Tero; Lepane, Viia; Pihlaja, KaleviTalanta2005 / p. 103-111 : ill https://www.sciencedirect.com/science/article/abs/pii/S0039914005001141 Elemental composition of humic and fulvic acids in the epipedon of some Estonian solidsReintam, Loit; Kann, Jüri; Kailas, Tiiu; Kährik, RajaProceedings of the Estonian Academy of Sciences. Chemistry2000 / 3, p. 131-144 https://artiklid.elnet.ee/record=b2397615*est Influence of bedrock composition on the content of biogenic elements in the humus horizon of soils in EstoniaSõstra, Ülo; Petersell, ValterIII международная конференция по лесному почвоведению : продуктивность и устойчивость лесных почв = III International Forest Soil Science Conference : Productivity and Resistance of Forest Soils : 7-11 сентября 2009, Г.Петрозаводск, Республика Карелия, Россия2009 / с. 37-38