Birkelbach, Jens, y Rodolfo Ortiz Vargas. 2012. «ELEMENT CONTENTS OF SOIL AND LEAVES AND THEIR CORRELATION IN FIVE TREE SPECIES IN AN AREA OF THE RESERVA BIOLOGICA ALBERTO BRENES, COSTA RICA». Pensamiento Actual 2 (2). https://revistas.ucr.ac.cr/index.php/pensamiento-actual/article/view/3928.