Update README.md

Add intro and reference, and one more link to NGC

README.md

@@ -18,6 +18,10 @@
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+[Megatron](https://arxiv.org/pdf/1909.08053.pdf) is a large, powerful transformer developed by the Applied Deep Learning Research team at NVIDIA. This particular Megatron model was trained from a generative, left-to-right transformer in the style of GPT-2. This model was trained on text sourced from Wikipedia, RealNews, OpenWebText, and CC-Stories. It contains 345 million parameters. 
+
+Find more information at [https://github.com/NVIDIA/Megatron-LM](https://github.com/NVIDIA/Megatron-LM)
+
 # How to run Megatron GPT2 using Transformers
 
 ## Prerequisites 
@@ -44,7 +48,7 @@ You must create a directory called `nvidia/megatron-gpt2-345m`:
 mkdir -p $MYDIR/nvidia/megatron-gpt2-345m
 ```
 
-You can download the checkpoints from the NVIDIA GPU Cloud (NGC). For that you
+You can download the checkpoints from the [NVIDIA GPU Cloud (NGC)](https://ngc.nvidia.com/catalog/models/nvidia:megatron_lm_345m). For that you
 have to [sign up](https://ngc.nvidia.com/signup) for and setup the NVIDIA GPU
 Cloud (NGC) Registry CLI.  Further documentation for downloading models can be
 found in the [NGC