 The Liturgy of St Tikhon was produced in the 1970s for use by Episcopalians who wished to convert to Orthodoxy but retain the liturgy to which they were accustomed.The text of the liturgy, therefore, is based upon the Episcopal Church's 1928 "Book of Common Prayer", along with certain features of the Tridentine Mass (the Mass of the Roman Catholic Church prior to its reform after the Second Vatican Council), as well certain modifications to make it conform to Orthodox theology and practice (such as a strengthened epiclesis, the omission of the filioque from the Nicene-Constantinopolitan Creed).The adaptation of the rite was the work of Father Joseph Angwin.