TY - JOUR TI - CJM volume 72 Issue 6 Cover and Front matter JO - Canadian journal of mathematics PY - 2020 SP - f1 EP - f2 VL - 72 IS - 6 UR - http://geodesic.mathdoc.fr/articles/10.4153/S0008414X20000401/ DO - 10.4153/S0008414X20000401 ID - 10_4153_S0008414X20000401 ER -