reference reference http://scienceline.ucsb.edu/getkey.php?key=1668 http://scienceline.ucsb.edu/getkey.php?key=1668 http://scienceline.ucsb.edu/getkey.php?key=1668 http://scienceline.ucsb.edu/getkey.php?key=1668 http://scienceline.ucsb.edu/getkey.php?key=1668 http://scienceline.ucsb.edu/getkey.php?key=1668 http://scienceline.ucsb.edu/getkey.php?key=1668 reference http://scienceline.ucsb.edu/getkey.php?key=1668 http://scienceline.ucsb.edu/getkey.php?key=1668 http://scienceline.ucsb.edu/getkey.php?key=1668 http://scienceline.ucsb.edu/getkey.php?key=1668 http://scienceline.ucsb.edu/getkey.php?key=1668