Sol-gel chemistry approach in the preparation of precursors for the substituted superconducting oxidesPleckis, G.; Tõnsuaadu, Kaia; Baubonyte, T.; Kareiva, AivarasJournal of non-crystalline solids2002 / p. 250-258https://www.sciencedirect.com/science/article/abs/pii/S0022309302013777