[doc] update README

README.md

@@ -99,7 +99,7 @@ assert tokens == [1, 7596, 1247, 28747, 26256, 2936, 7653, 1413, 334, 1680, 3200
 | Open-source SOTA** | 13B-70B  | 61.4     | 7.71         | 41.7     | 49.7     | 62.3          | 63.7         | 73.2            | 41.4        | 82.3         |
 |                    |          |          | WizardLM 70B | Orca 13B | Orca 13B | Platypus2 70B | WizardLM 70B | WizardCoder 34B | Flan-T5 11B | MetaMath 70B |
 
-*: ChatGPT (March) results are from GPT-4 Technical Report, Chain-of-Thought Hub, and our evaluation.
+*: ChatGPT (March) results are from [GPT-4 Technical Report](https://arxiv.org/abs/2303.08774), [Chain-of-Thought Hub](https://github.com/FranxYao/chain-of-thought-hub), and our evaluation. Please note that ChatGPT is not a fixed baseline and evolves rapidly over time.
 
 **: Open-source SOTA results are taken from reported results in instruction-tuned model papers and official repositories.