[1] Univ Saskatchewan, Dept Math & Stat, Saskatoon, SK S7N 5E6, Canada
[2] York Univ, Dept Math & Stat, Toronto, ON M3J 1P3, Canada
[3] Univ British Columbia, Dept Stat, Vancouver, BC V6T 1Z4, Canada
[4] Univ New Brunswick, Dept Math & Stat, Fredericton, NB E3B 5A3, Canada