Morfologiya i sistematicheskoe polozhenie Virucrinus Rozhnov gen. nov. (Crinoidea, Inadunata, Disparida) iz srednego ordovika severnoi Estonii [Morphology and systematic position of Middle Ordovician Virucrinus Rozhnov gen. nov. (Crinoidea, Inadunata, Disparida) from north Estonia] - 1990