[README] Add Unity paper

Author: jiazhihao

README.md

@@ -108,9 +108,11 @@ We welcome all contributions to FlexFlow from bug fixes to new features and exte
 Please subscribe to the FlexFlow users mailing list for 
 
 ## Citations
-* Zhihao Jia, Matei Zaharia, and Alex Aiken. [Beyond Data and Model Parallelism for Deep Neural Networks](https://cs.stanford.edu/~zhihao/papers/sysml19a.pdf). In Proceedings of the 2nd Conference on Machine Learning and Systems (MLSys), Palo Alto, CA, April 2019.
+* Colin Unger, Zhihao Jia, Wei Wu, Sina Lin, Mandeep Baines, Carlos Efrain Quintero Narvaez, Vinay Ramakrishnaiah, Nirmal Prajapati, Pat McCormick, Jamaludin Mohd-Yusof, Xi Luo, Dheevatsa Mudigere, Jongsoo Park, Misha Smelyanskiy, and Alex Aiken. [Unity: Accelerating DNN Training Through Joint Optimization of Algebraic Transformations and Parallelization](https://www.usenix.org/conference/osdi22/presentation/unger). In Proceedings of the Symposium on Operating Systems Design and Implementation (OSDI), July 2022. 
 
-* Zhihao Jia, Sina Lin, Charles R. Qi, and Alex Aiken. [Exploring Hidden Dimensions in Parallelizing Convolutional Neural Networks](http://proceedings.mlr.press/v80/jia18a/jia18a.pdf). In Proceedings of the International Conference on Machine Learning (ICML), Stockholm, Sweden, July 2018.
+* Zhihao Jia, Matei Zaharia, and Alex Aiken. [Beyond Data and Model Parallelism for Deep Neural Networks](https://cs.stanford.edu/~zhihao/papers/sysml19a.pdf). In Proceedings of the 2nd Conference on Machine Learning and Systems (MLSys), April 2019.
+
+* Zhihao Jia, Sina Lin, Charles R. Qi, and Alex Aiken. [Exploring Hidden Dimensions in Parallelizing Convolutional Neural Networks](http://proceedings.mlr.press/v80/jia18a/jia18a.pdf). In Proceedings of the International Conference on Machine Learning (ICML), July 2018.
 
 ## The Team
 FlexFlow is developed and maintained by teams at CMU, Facebook, Los Alamos National Lab, MIT, and Stanford (alphabetically).