• Variation in the composition of the essential oils, phenolic compounds and mineral elements of Hypericum perforatum L. growing in EstoniaHelmja, Kati; Vaher, Merike; Püssa, Tõnu; Orav, Anne; Viitak, Anu; Levandi, Tuuli; Kaljurand, MihkelNatural product research2011 / p. 496-510