protected function setHeadingIds( &$content, $level = 1 ){
		foreach( $this->headings as $heading ){														//  
			$find		= "/<h".$heading->level."(.*)>".$heading->label."/";						//  
			$replace	= '<h'.$heading->level.'\\1 id="'.$heading->id.'">'.$heading->label;		//  
			$content	= preg_replace( $find, $replace, $content );								//  
		}
		return $content;
	}