1. Morris, R.J. (1988). Sulphur - the fourth major plant nutrient, Proc. of International Symposium on “Sulphur for Korean agriculture”, Seoul, Korea, Proc. 9-16.
4. Krzywy, J., Krzywy, E., Krzywy-Gawrońska, E. & Rozmarynowska, M. (2007). The effect of sewage sludge composts and potato pulp on uptaking of macroelements by the grain and straw of the spring triticale. Pol. J. Chem. Tech., 9(4), 14-17. DOI: 10.2478/v/10026-007-0081-0.
6. Krzywy, E., Możdżer, E. & Iżewska, A. (2012). Research on the use of industrial wastes for the production of organic and mineral fertilizers and their impact on soil fertility. Sprawozdanie końcowe z badań przeprowadzonych w ramach projektu badawczego MNiSW NN 305 155136, ss. 70. [in Polish].
11. Krzywy, E., Wołoszyk, Cz., Głowacka, A., & Krzywy, J. (1998). Studies of FeSO4 ∙ 7H2O action against the amount of fertilizers and crop quality characteristics of some plants. Part I mix reclamation grasses. Folia Univ. Agric. Stetin., Agriculturae (190)72, 159-162 [in Polish].
12. Krzywy, E. & Jakubowski, W. (2000). Effect of FeSO4 ∙ 7H2O waste phosphogypsum and the sulfur content in the soil, iron, cadmium and nickel. Zesz. Probl. Nauk Rol. 472, 443-448 [in Polish].
13. Pasikowski, K. (2000). Studies on the use of 7 hydrate (VI) iron (II) for use as fertilizers. Praca doktorska. Akad. Rol. Szczec. ss. 86 [in Polish].
14. Krzywy, J. (2001). Measure residual sulfate (VI) iron (II) to yield a mixture of grasses, and on the enzymatic activity of the soil. Uniwersytet Warmińsko-Mazurski w Olsztynie. Praca doktorska, ss. 86 [in Polish].
15. Krzywy, E., Krzywy, J. & Krzywy-Gawrońska, E. (2005). The infl uence of foliar fertilization by water solution of 7 hydrate sulphate(VI) iron(II) on yielding and chemical composition of cropsi. I. The infl uence of foliar fertilization with water solution of 7 hydrate sulphate(VI) iron(II) on crops yield quantity. Pol. J. Chem. Tech., 7, 16-18.
16. Krzywy, E., Krzywy, J. & Krzywy-Gawrońska, E. (2005). The infl uence of foliar fertilization by water solution of 7 hydrate sulphate(VI) iron(II) on yielding and chemical composition of cropsi. II. The infl uence of foliar fertilization with water solution of 7 hydrate sulphate(VI) iron(II) on content of nitrogen, phosphorus, potassium, calcium, magnesium, sulphur and iron in plants. Pol. J. Chem. Tech., 7, 19-21.
17. Rozmarynowska, M. (2009). Research on the effects of foliar sulfur and iron by-product of FeSO4 ∙ 7H2O on the quantity and quality characteristics of crop plants. Praca doktorska. Zachodniopomorski Uniwersytet Technologiczny w Szczecinie ss.119 [in Polish].
19. Baran, S. (2005). Resources and organic waste management in Poland. Selected aspects of organic waste and biomass production of willow. Wyd. Uniw. Rzeszow., Rzeszów: 17-40 [in Polish].
20. Kalembasa, S. (2003). Agricultural use of sewage sludge. W:substancje humusowe w glebach i nawozach. Pod red. C. Dąbskiej i S.S. Goneta, Wrocław P.T.S/H.S.:63-74.
22. Krzywy, E., Wołoszyk, C. & Iżewska, A. (2002). Production and agricultural use of sewage sludge compost with the addition of the various components. Wyd. PTIE Oddział Szczeciński: 39 [in Polish].
23. Łabętowicz, J. & Stępień, W. (2011). Conditions of recycling waste in the environment. W:Przyrodnicze wykorzystanie odpadów. Wyd. PWRiL Warszawa:11-34 [in Polish].
27. Krzywy, E., Krzywy-Gawrońska, E., Krzywy, J. & Wołoszyk, C. (2007). Impact of composts with participation of municipal sewage sludge on content of available forms of phosphorus for plants and on quantity of spring rape seed yield. Pol. J. Chem. Tech. 9(4), 98-101. DOI: 10.2478/v/10026-007-0099-3.
28. Krzywy-Gawrońska, E. (2006). Changes in pH and macronutrient content in composts from potato pulp, straw, sawdust, and municipal sewage sludge during their decomposition. Zesz. Probl. Post. Nauk Rol. 512, 369-379 [in Polish].
29. Krzywy-Gawrońska, E. & Gutkowska, I. (2007). The content of macro-and micronutrients in perennial ryegrass on the use of compost in potato pulp and municipal sewage sludge. Wyd. IMUZ Raszyn, Czasopismo „Woda, środowisko, obszary wiejskie” 7 z 2a (20), 231-244 [in Polish].