function MsPowerpoint_Clean(&$Txt) {
		$this->MsPowerpoint_CleanRpr($Txt, 'a:rPr');
		$Txt = str_replace('<a:rPr/>', '', $Txt);

		$this->MsPowerpoint_CleanRpr($Txt, 'a:endParaRPr');
		$Txt = str_replace('<a:endParaRPr/>', '', $Txt); // do not delete, can change layout

		// join split elements
		$Txt = str_replace('</a:t><a:t>', '', $Txt);
		$Txt = str_replace('</a:t></a:r><a:r><a:t>', '', $Txt); // this join TBS split tags

		// delete empty elements
		$Txt = str_replace('<a:t></a:t>', '', $Txt);
		$Txt = str_replace('<a:r></a:r>', '', $Txt);
	}