update README

README.md

@@ -30,8 +30,8 @@ alt="Mobile platform" width="240" height="180" border="10" /></a>
  MAV application;               Mobile implementation (Video link for mainland China friends: [Video1](http://www.bilibili.com/video/av10813254/) [Video2](http://www.bilibili.com/video/av10813205/) [Video3](http://www.bilibili.com/video/av10813089/) [Video4](http://www.bilibili.com/video/av10813325/) [Video5](http://www.bilibili.com/video/av10813030/))
 
 **Related Papers**
-* **VINS-Mono: A Robust and Versatile Monocular Visual-Inertial State Estimator**, Tong Qin, Peiliang Li, Zhenfei Yang, Shaojie Shen [arXiv:1708.03852](https://arxiv.org/abs/1708.03852v1) 
-* **Autonomous Aerial Navigation Using Monocular Visual-Inertial Fusion**, Yi Lin, Fei Gao, Tong Qin, Wenliang Gao, Tianbo Liu, William Wu, Zhenfei Yang, Shaojie Shen, J Field Robotics. 2017;00:1–29. [https://doi.org/10.1002/rob.21732](https://doi.org/10.1002/rob.21732)  
+* **VINS-Mono: A Robust and Versatile Monocular Visual-Inertial State Estimator**, Tong Qin, Peiliang Li, Zhenfei Yang, Shaojie Shen, IEEE Transactions on Robotics[pdf](https://ieeexplore.ieee.org/document/8421746/?arnumber=8421746&source=authoralert) 
+
 ```
 @article{qin2017vins,
   title={VINS-Mono: A Robust and Versatile Monocular Visual-Inertial State Estimator},