Ziziphus jujube Bronnen
| 5 | Crawford, M. (2010). Creating a forest garden. Green books. |
| 6 | Crawford, M. (2020). Shrubs for gardens, agroforestry and permaculture. Permanent Publications. |
| 11 | Jacke, D., & Toensmeier, E. (2005). Edible forest gardens, volume II: ecological design and practice for temperate-climate permaculture (Vol. 2). Chelsea Green Publishing. |