In his letter to bishops which accompanied his 2007 motu proprio "Summorum Pontificum", Pope Benedict XVI wrote that "the Missal published by Paul VI and then republished in two subsequent editions by John Paul II, obviously is and continues to be the normal Form – the "Forma ordinaria" – of the Eucharistic Liturgy." Since then, the term "Ordinary Form" (abbreviated OF) is often used to distinguish this form of the Roman Rite of Mass from the 1962 edition of the Tridentine Mass, often called the "Extraordinary Form" (EF), because in his motu proprio Pope Benedict declared it an extraordinary form of the Roman Rite.