Yttrium and all lanthanides except Ce and Pm have been observed in the oxidation state 0 in bis(1,3,5-tri-t-butylbenzene) complexes, see Cloke, F. Geoffrey N. Zero Oxidation State Compounds of Scandium, Yttrium, and the Lanthanides. Chem. Soc. Rev. 1993, 22: 17–24. doi:10.1039/CS9932200017. and Arnold, Polly L.; Petrukhina, Marina A.; Bochenkov, Vladimir E.; Shabatina, Tatyana I.; Zagorskii, Vyacheslav V.; Cloke. Arene complexation of Sm, Eu, Tm and Yb atoms: a variable temperature spectroscopic investigation. Journal of Organometallic Chemistry. 2003-12-15, 688 (1–2): 49–55. doi:10.1016/j.jorganchem.2003.08.028.
Per Teodor Cleve. Sur deux nouveaux éléments dans l'erbine. Comptes rendus de l'Académie des sciences. 1879, 89: 478–480 [2021-06-06]. (原始內容存檔於2021-06-25). Cleve named holmium on p. 480: "Je propose pour ce métal le nom de holmium, Ho, dérivé du nom latinisé de Stockholm, dont les environs renferment tant de minéraux riches en yttria." (I propose for this metal the name of "holmium", Ho, [which is] derived from the Latin name for Stockholm, the environs of which contain so many minerals rich in yttrium.)
Wollin, T. A.; Denstedt, J. D. The holmium laser in urology. Journal of Clinical Laser Medicine & Surgery. Feb 1998, 16 (1): 13–20. PMID 9728125. doi:10.1089/clm.1998.16.13.
Forrester, Patrick Robert; Patthey, François; Fernandes, Edgar; Sblendorio, Dante Phillipe; Brune, Harald; Natterer, Fabian Donat. Quantum state manipulation of single atom magnets using the hyperfine interaction. Physical Review B. 2019-11-19, 100 (18): 180405. Bibcode:2019PhRvB.100r0405F. ISSN 2469-9950. doi:10.1103/PhysRevB.100.180405(英語).