Thomas A. Carlson (ed.), "Tigris Valley" in last modified January 14, 2014, http://syriaca.org/place/786
    
        
            
                
                    Tigris Valley
                    The valley of the Tigris river.
                    
                        Gāzartā region
                    
          
                    http://syriaca.org/place/786
                    
                        David Wilmshurst
                        The Ecclesiastical Organisation of the Church of the East, 1318-1913
                        111, 117-118