Proper Mass texts for Blessed John XXIII, Pope
The General Instruction of the Roman Missal
The Choice of the Mass and its Parts
On weekdays in Ordinary Time, there may be chosen either the Mass of the…
355 On Optional Memorials:
c. weekday, or the Mass of an Optional Memorial which happens to occur on that day, or the Mass of any Saint inscribed in the Martyrology for that day, or a Mass for Various Needs, or a Votive Mass.
If he celebrates with the people, the Priest will take care not to omit too frequently and without sufficient reason the readings assigned each day in the Lectionary to the weekdays, for the Church desires that a richer portion at the table of God’s Word should be spread before the people.141
141 Cf. Second Ecumenical Council of the Vatican, Constitution on the Sacred Liturgy, Sacrosanctum Concilium, no. 51.