Catechism of the Catholic Church §1206 — excerpt
"Liturgical diversity can be a source of enrichment, but it can also provoke tensions, mutual misunderstandings, and even schisms. In this matter it is clear that diversity must not damage unity.
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.
Also cites: John Paul 11, Vicesimus quintus annus, 16