Update README.md

Author: ttdtrang

README.md

@@ -1,2 +1,11 @@
 # gbnorm - A graph-based algorithm for RNA-seq data normalization
 
+Citation: Tran DT, Bhaskara A, Kuberan B, Might M (2020) A graph-based algorithm for RNA-seq data normalization. PLOS ONE 15(1): e0227760. https://doi.org/10.1371/journal.pone.0227760
+
+## Notes
+
+* [Release v0.99](https://github.com/ttdtrang/gbnorm/releases/tag/v0.99) is the first working snapshot of gbnorm. This version was used in the paper https://doi.org/10.1371/journal.pone.0227760. In this implementation, all the functions taking expression matrix as an input assume that features (genes/transcripts) are in columns and samples are in rows.
+
+## License
+
+GNU GPLv3