Due to the lanthanide contraction phenomenon, the REE are further divided into larger LREE (light Ln, La–Sm), medium MREE (Sm–Dy) and smaller HREE (heavy Ln, Tb–Lu and Y). 2024, Martin Ondrejka, Peter Bačík, Juraj Majzlan, Pavel Uher, Štefan Ferenc, Tomáš Mikuš, Martin Števko, Mária Čaplovičová, Stanislava Milovská, Alexandra Molnárová, Christiane Rößler, Christian Matthes, “Xenotime-(Gd), a new Gd-dominant mineral of the xenotime group from the Zimná Voda REE–U–Au quartz vein, Prakovce, Western Carpathians, Slovakia”, in Mineralogical Magazine, volume 88, number 5: