Affiliation: | 1 Department of Biostatistics, Columbia University School of Public Health, 722 West 168 Street, Room 637, New York, New York 10032, U.S.Aydu{at}biostat.cpmc.columbia.edu 2 Department of Statistics, Penn State University, University Park, Pennsylvania 16802, U.S.A.mga{at}stat.psu.edu 3 Institute of Statistics, Université Catholique de Louvain, B-1348 Louvain-la-Neuve, Belgiumvankeilegom{at}stat.ucl.ac.be |