Add CSS to Thesis via the CSS filter

gistfile1.php

<?php

// add css using the thesis_css filter

class your_skin_class extends thesis_skin {
	
	function construct() {
		add_filter('thesis_css', array($this, 'add_css'));
	}
	
	function add_css($css) {
		$import = "@import url(http://fonts.googleapis.com/css?family=Lora|Oswald);\n";
		$css = $import . $css;
		return $css;
	}
}