- http://www.paris.fr/portail/Culture/Musée Zadkine, Paris
- http://www.pieter-wiegersma.comPieter Wiegersma b.1920
- http://www.tjerk-wiegersma.comWFA - Wiegersma Fine Art
- http://www.jules-cavailles.comJules Cavailles Research Center
- http://www.jan-toorop.comJan Toorop Research Center
- http://www.catherine-roisin.comCatherine Roisin