Add DIRECT JOSS citation to model card

README.md

@@ -81,6 +81,26 @@ The first argument is the **prediction output directory**.
 
 ## Citation
 
+If you use these models or [DIRECT](https://github.com/NKI-AI/direct), please cite the DIRECT toolkit and the method paper(s) below.
+
+### DIRECT
+
+```bibtex
+@article{DIRECTTOOLKIT,
+  title={DIRECT: Deep Image REConstruction Toolkit},
+  author={Yiasemis, George and Moriakov, Nikita and Karkalousos, Dimitrios and Caan, Matthan and Teuwen, Jonas},
+  journal={Journal of Open Source Software},
+  volume={7},
+  number={73},
+  pages={4278},
+  year={2022},
+  doi={10.21105/joss.04278},
+  url={https://doi.org/10.21105/joss.04278}
+}
+```
+
+### Method
+
 ```bibtex
 @inproceedings{moriakov2026modconv,
   title={Conditional Learned Reconstruction for Medical Imaging},