1. Department of StatisticsStanford University Stanford CA 94305 U.S.A.
2. Hautes Etudes Chretiennes de Management et de Mathematiques Appliquees (HECMMA) Antananarivo Madagascar
3. Department of Mathematics & StatisticsMissouri University of Science and Technology Rolla MO 65409‐0020 U.S.A.
4. Department of Mathematics & StatisticsTexas Tech University Lubbock TX 79409‐1042 U.S.A.