Department of Statistics, Rice University, 6100 Main, Houston, TX 77005-1827, USA.|Department of Statistics, Rice University, 6100 Main, Houston, TX 77005-1827, USA.|Department of Statistics, Rice University, 6100 Main, Houston, TX 77005-1827, USA.|Department of Statistics, Rice University, 6100 Main, Houston, TX 77005-1827, USA.|Department of Statistics, Rice University, 6100 Main, Houston, TX 77005-1827, USA.|Department of Statistics, Rice University, 6100 Main, Houston, TX 77005-1827, USA.