used in the Liturgy of the Hours, nor were the preface (if "proper") of the commemorated feast and the Credo, if the commemorated feast had a right to it, to be used in Mass. Five years later, the Code of Rubrics, which was composed by the same commission that had prepared the decree Cum nostra hac aetate, added little. It distinguished between privileged commemorations, i. e. those that in Cum nostra hac aetate were always to be made, with the addition of days within the Octave of Christmas, and ordinary commemorations. Privileged commemorations were to be made in Lauds and Vespers and all Masses, ordinary commemorations only in Lauds and conventual and low Masses. It also limited ordinarily to First-Class Feasts the celebration of First Vespers. After the Second Vatican Council The Liturgy of the Hours and Roman Missal as revised after the Second Vatican Council have greater flexibility on most days of the year, allowing a choice between several celebrations, each making no mention of any other alternative celebration. Only a few saints are classified in the General Roman Calendar as solemnities or feasts; the remainder are memorials, most of them optional. On optional memorials, Mass may be of the weekday (feria) or of one of the saints listed as optional memorials or of any saint inscribed in the Roman Martyrology for that day. The choice is more limited on the weekdays of Advent from 17 to 24 December, on the days within the Octave of Christmas, and on the weekdays of Lent. On those days the Mass of the current liturgical day must be used, but the collect may be taken from a memorial of the day, except on Ash Wednesday and during Holy Week. The Liturgy of the Hours as revised by Pope Paul VI and promulgated in 1970 prescribes that on the days when in Mass the collect is the only part of a memorial that may be used one may: after the patristic reading with its responsory from the proper of the season in the Office of Readings, add the proper hagiographical reading with a responsory and conclude with the prayer of the saint; after the concluding prayer in Lauds and Vespers, add the antiphon (proper or else from the common) and prayer of the saint. This optional arrangement on such days in Mass and in the Liturgy of the Hours has obvious similarities with