_accent_map = {
        r'hat'   : r'\circumflexaccent',
        r'breve' : r'\combiningbreve',
        r'bar'   : r'\combiningoverline',
        r'grave' : r'\combininggraveaccent',
        r'acute' : r'\combiningacuteaccent',
        r'tilde' : r'\combiningtilde',
        r'dot'   : r'\combiningdotabove',
        r'ddot'  : r'\combiningdiaeresis',
        r'vec'   : r'\combiningrightarrowabove',
        r'"'     : r'\combiningdiaeresis',
        r"`"     : r'\combininggraveaccent',
        r"'"     : r'\combiningacuteaccent',
        r'~'     : r'\combiningtilde',
        r'.'     : r'\combiningdotabove',
        r'^'     : r'\circumflexaccent',
        r'overrightarrow' : r'\rightarrow',
        r'overleftarrow'  : r'\leftarrow',
        r'mathring' : r'\circ'
        }

    _wide_accents = set(r"widehat widetilde widebar".split())