The day the Church abandons her universal tongue [Latin] is the day before she returns to the catacombs. Pope Pius XII

EXCERPTS FROM VATICAN II ON THE USE OF LATIN IN THE LITURGY

You may also want to view the entirety of Sacrosanctum Consilium, which is the Second Vatican Council document concerning the reform of the Roman liturgy.

Sacrosanctum Concilium, #4; December 4, 1963

"Lastly, in faithful obedience to tradition, the sacred Council declares that holy Mother Church holds all lawfully acknowledged rites to be of equal right and dignity; that she wishes to preserve them in the future and to foster them in every way."

Sacrosanctum Concilium, #36; December 4, 1963

“. . .the use of the Latin language is to be preserved in the Latin rites."

Sacrosanctum Concilium, #116; December 4, 1963

"The Church acknowledges Gregorian chant as specially suited to the Roman liturgy: therefore, other things being equal, it should be given pride of place in liturgical services."

Orientalium Ecclesiarum, #2; November 21, 1964

[From the Second Vatican Council document concerning the Eastern Rite Churches.]

"The Holy Catholic Church, which is the Mystical Body of Christ, is made up of the faithful who are organically united in the Holy Spirit by the same faith, the same sacraments and the same government and who, combining together into various groups which are held together by a hierarchy, form separate churches or Rites. Between these there exists an admirable bond of union, such that the variety within the Church in no way harms its unity; rather it manifests it, for it is the mind of the Catholic Church that each individual Church or Rite should retain its traditions whole and entire and likewise that it should adapt its way of life to the different needs of time and place."