Sacrosanctum Concilium §40

⁴⁰ In some places and circumstances, however, an even more radical adaptation of the liturgy is needed, and this entails greater difficulties. Wherefore: 1) The competent territorial ecclesiastical authority mentioned in Art. 22, 2, must, in this matter, carefully and prudently consider which elements from the traditions and culture of individual peoples might appropriately be admitted into divine worship. Adaptations which are judged to be useful or necessary should then be submitted to the Apostolic See, by whose consent they may be introduced. 2) To ensure that adaptations may be made with all the circumspection which they demand, the Apostolic See will grant power to this same territorial ecclesiastical authority to permit and to direct, as the case requires, the necessary preliminary experiments over a determined period of time among certain groups suited for the purpose. 3) Because liturgical laws often involve special difficulties with respect to adaptation, particularly in mission lands, men who are experts in these matters must be employed to formulate them. E) Promotion of Liturgical Life in Diocese and Parish