code: Rule IfieldLyrics() {
  		return Sequence(String("[w:"),
  				ZeroOrMore(WSP()).suppressNode(),
  				TexTextIfield(), //TODO Lyrics() ?
  				String("]"))
  			.label(IfieldLyrics);
  	}
docs: ifield-lyrics ::= %5B.%77.%3A *WSP tex-text-ifield %5D<p>
  <tt>[w:..]</tt>