Update README.md

Added link and reference to paper (preprint)

README.md

@@ -37,7 +37,7 @@ The ManyWells datasets contain simulations of multiphase (gas, oil, water) flow
 - **Curated and shared by:** [Solution Seeker AS](https://www.solutionseeker.no)
 - **License:** Creative Commons BY-NC 4.0
 - **Code repository:** [ManyWells GitHub repository](https://github.com/solution-seeker-as/manywells)
-- **Paper:** [Coming soon]
+- **Paper:** [ManyWells paper (preprint)](https://ssrn.com/abstract=5256125)
 
 ## Description of datasets
 
@@ -119,13 +119,26 @@ df = data['train'].to_pandas()
 print(df)
 ```
 
-## Citation [coming soon]
+## Citation
 
-We kindly ask that you cite our paper if you use the ManyWells datasets or code in your academic work.
+We kindly ask that you cite our paper if you use the ManyWells datasets or code in your academic work. 
+
+Note that the paper is currently in review and that the reference below is to a preprint.
 
 **BibTeX:**
 
-[Coming soon]
+```
+@article{Grimstad2025,
+	title = {{ManyWells: Simulation of Multiphase Flow in Thousands of Wells}},
+	author = {Grimstad, Bjarne and Lundby, Erlend and Andersson, Henrik},
+	journal = {SSRN Electronic Journal},
+	issn = {1556-5068},
+	doi = {10.2139/ssrn.5256125},
+	year = {2025},
+	pages = {1--47},
+	note = {Preprint}
+}
+```
 
 
 ## Dataset contact