Institute of Statistical Science, Academia Sinica, Taipei, 11529, Taiwan. gary@stat.sinica.edu.tw|Institute of Statistical Science, Academia Sinica, Taipei, 11529, Taiwan. gary@stat.sinica.edu.tw|Institute of Statistical Science, Academia Sinica, Taipei, 11529, Taiwan. gary@stat.sinica.edu.tw|Institute of Statistical Science, Academia Sinica, Taipei, 11529, Taiwan. gary@stat.sinica.edu.tw