Paper:
Improving the sample efficiency in reinforcement learning has been a longstanding research problem. In this work, we aim to reduce the sample complexity of existing policy gradient methods. We propose a novel policy gradient algorithm called SRVR-PG, which only requires O(1/ 3/2 ) 1 episodes to find anapproximate stationary point of the nonconcave performance function J(θ) (i.e., θ such that ∇J(θ) 2 2 ≤ ). This sample complexity improves the existing result O(1/ 5/3 ) for stochastic variance reduced policy gradient algorithms by a factor of O(1/ 1/6 ). In addition, we also propose a variant of SRVR-PG with parameter exploration, which explores the initial policy parameter from a prior probability distribution. We conduct numerical experiments on classic control problems in reinforcement learning to validate the performance of our proposed algorithms.

Review:
Summary: 
The paper proposed a policy gradient method called SRVR-PG, which based on stochastic recursive gradient estimator. It shows that the complexity is better than that of SVRPG. Some experiments on standard environments are provided to show the efficiency of the algorithm over GPOMDP and SVRPG.   
Comments:
1) I think you may ignore the highly-related work: Yang and Zhang, "Policy Optimization with Stochastic Mirror Descent", June 2019. Since both papers are highly-related, I would suggest the author(s) have some discussions to differentiate two papers. 
2) Could you please provide the reasons why you are only choosing two methods (GPOMDP and SVRPG) to compare? There are many policy gradient algorithms such as A3C, A2C, ... which have not mentioned or discussed in this paper. Are they completely different here? Is there no way to compare the performance among them with SRVR-PG? 
3) I am not sure if you are using the right word "novel" to describe your method. Basically, you adopt the existing estimator based on SARAH/SPIDER in optimization algorithms into RL problems. I do not think the word "novel" is proper here since it is not something total new. Notice that, the complexity result achieved in this paper is also matched the one for SARAH/SPIDER/SpiderBoost in nonconvex optimization. 
4) There are some discussion on choosing a batch-size in the experimental part. However, I do not see the discussion on the learning rate. The choice of parameters for GPOMDP and SVRPG may also need to be discussed. 
5) In Papini et al., 2018, for the experiment part, they use a snapshot policy to sample in the inner loop, and use early stopping inner loop. Moreover, they also check variance to recover the backup policy when it is blowup. Do you apply any trick to your experiments? I wonder if your numerical experiments are totally followed on your theory. 
Minor comments: 
- Redundancy ")" in \eta*S*m in Theorem 4