Synthesis and caharacterization of a tetramethylurea adduct of a biscyclopentadienyl ytterium (ii) complex x-ray crystal structure of ybc 'P IND.2'.2 tmu - Silva-Valenzuela, M G; Zinner, Lea Barbieri; Domingos, A; Marques, Nélson; Matos, A P (International Conference on F-Elements, 1994)