Halbach, Peter (1975): Observation of manganese nodules and encrustations in various lakes of Finland [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.864229, Supplement to: Halbach, P (1976): Mineralogical and geochemical investigations on Finnish lake ores. Bulletin of the Geological Society of Finland, 48(1-2), 33-42, https://doi.org/10.17741/bgsf/48.1-2.004