Prof. Dr. D. Jordi-Agustí Piqué i Collado OSB, Benedictine monk of the Montserrat Abbey, Catalonia-Spain, Dean of the Pontificio Istituto Liturgico, Roma, Italy, Invited Professor in the Facultat de Teologia de Catalunya, Barcelona, Spain. Address: Pontificio Istituto Liturgico, Piazza Cavalieri di Malta 5, 00153 Roma, Italia