In iconography, the evangelists often appear in Evangelist portraits derived from classical tradition, and are also frequently represented by the symbols which originate from the four "living creatures" that draw the throne-chariot of God, the Merkabah, in the vision in the Book of Ezekiel (Chapter 1) reflected in the Book of Revelation (ff), referred to as the four 'Seraphims', though neither source links the creatures to the Evangelists (of course the depiction of the Seraphims predates in chronology the writing of the new testaments books which portrays the writers John, Luke, Mark, Matthew as symbolically emodied by the four Seraphims ). Images normally, but not invariably, appear with wings like angels. When the symbols of the Four Evangelists appear together, it is called a Tetramorph, and is common in the Romanesque art of Europe, in church frescoes or mural paintings, for instance.