North American Western Rite parishes in the Antiochian Western Rite Vicariate generally follow one of two types of traditional Western liturgical traditions (and sometimes both). The majority celebrate the Liturgy of St. Tikhon of Moscow, which is commonly accepted to be an adaptation of the Communion service from the 1928 Anglican Book of Common Prayer and The Anglican Missal in the American Edition. Until 1977, all Western Rite Vicariate parishes celebrated only the Liturgy of St. Gregory the Great, which is a modified form of the Tridentine Mass (that is, the Mass as revised and authorized by the Roman Catholic Council of Trent). Many parishes within the Western Rite Vicariate continue to celebrate the Gregorian liturgy. Since most AWRV parishes celebrate more than one weekly liturgy, many of the parishes that celebrate the Liturgy of St. Tikhon on Sunday celebrate the Liturgy of St. Gregory on weekdays