Update README.md with citation

README.md

@@ -10,6 +10,7 @@
 * [Getting Started](#getting-started)
   * [Installation](#installation)
 * [Usage](#usage)
+* [Citation](#citation)
 * [Contributing](#contributing)
 * [Contact](#contact)
 
@@ -112,6 +113,27 @@ class Action(Enum):
 ```
 
 
+<!-- CITATION -->
+## Citation
+1. A comperative evaluation of MARL algorithms that includes this environment
+```
+@article{papoudakis2020comparative,
+  title={Comparative Evaluation of Multi-Agent Deep Reinforcement Learning Algorithms},
+  author={Papoudakis, Georgios and Christianos, Filippos and Sch{\"a}fer, Lukas and Albrecht, Stefano V},
+  journal={arXiv preprint arXiv:2006.07869},
+  year={2020}
+}
+```
+2. A method that achieves state-of-the-art performance in many Level-Based Foraging tasks
+```
+@inproceedings{christianos2020shared,
+  title={Shared Experience Actor-Critic for Multi-Agent Reinforcement Learning},
+  author={Christianos, Filippos and Sch{\"a}fer, Lukas and Albrecht, Stefano V},
+  booktitle = {Advances in Neural Information Processing Systems},
+  year={2020}
+}
+```
+
 
 <!-- CONTRIBUTING -->
 ## Contributing
@@ -124,6 +146,7 @@ Contributions are what make the open source community such an amazing place to b
 4. Push to the Branch (`git push origin feature/AmazingFeature`)
 5. Open a Pull Request
 
+
 <!-- CONTACT -->
 ## Contact