Biography Keppel
- Curriculum Vitae, compiled by Joop van Keppel
- Joop van Keppel Vicepresident of the National Cactus and Succulent Society
- In memoriam Joop van Keppel (Succulenta 62(3), 1983)
- In memoriam Joop van Keppel (Succulenta 62(3), 1983) - English translation
- In memoriam Joop van Keppel by Gordon Rowley (BCSJ 1(2), 1983)