Update README.md (#82)

Author: astomodynamics

README.md

@@ -142,9 +142,10 @@ If you want to use this library for ROS2 MPC node, please refer [CDDP MPC Packag
 ## References
 * Z. Xie, C. K. Liu and K. Hauser, "Differential dynamic programming with nonlinear constraints," 2017 IEEE International Conference on Robotics and Automation (ICRA), 2017, pp. 695-702, doi: <10.1109/ICRA.2017.7989086>.
 * Y. Tassa, N. Mansard and E. Todorov, "Control-limited differential dynamic programming," 2014 IEEE International Conference on Robotics and Automation (ICRA), 2014, pp. 1168-1175, doi: <10.1109/ICRA.2014.6907001>.
+* Pavlov, A., Shames, I., and Manzie, C., “Interior Point Differential Dynamic Programming,” IEEE Transactions on Control Systems Technology, Vol. 29, No. 6, 2021, pp. 2720–2727.
 * Zhamming Xie's GitHub repository: <https://github.com/ZhaomingXie/CDDP>
-* ZJU FAST Lab's GitHub repository: <https://github.com/ZJU-FAST-Lab/SDQP>
 * Yuval Tassa's iLQG/DDP trajectory optimization: <https://www.mathworks.com/matlabcentral/fileexchange/52069-ilqg-ddp-trajectory-optimization>
+* Andrei Pavlov's GitHub repository: <https://github.com/xapavlov/ipddp>
 
 ## Third Party Libraries