Traditionally, the essential defining criterion of Celticity is seen as "peoples and countries that do, or once did, use Celtic languages" and it is asserted that an index of connectedness to the Celtic languages has to be borne in mind before branching out into other cultural domains. Another approach to defining "the Celts" is the contemporary inclusive and associative definition used by Vincent and Ruth Megaw (1996) and Raimund Karl (2010) that a Celt is someone who uses a Celtic language or produces or uses a distinctive Celtic cultural expression (such as art or music) or has been referred to as a Celt in historical materials or has identified themselves or been identified by others as a Celt or has a demonstrated descent from the Celts (such as family history or DNA ancestry).