Šivel, M. ., Fišera, M. ., Klejdus, B. ., Kráčmar, S. ., Kubáň, V. ., Golian, J. . and Svobodová, B. . (2014) “Lutein in food supplements available on the markets of the Viszegrad countries”, Potravinarstvo Slovak Journal of Food Sciences, 8(1), pp. 261–266. doi: 10.5219/387.