doc(README): fix broken links

Author: Damian Rouson

README.md

@@ -116,6 +116,9 @@ Donate
 If you find this software useful, please consider donating code or
 [currency](http://bit.ly/donate-to-sourcery-institute) to aid in development efforts.
 
+[NASA Langley Research Center]: https://www.nasa.gov/langley
+[latest release]: https://github.com/sourceryinstitute/dag/releases/latest
+
 [daglib by Jacob Williams]: https://github.com/jacobwilliams/daglib
 [GraphViz]: https://www.graphviz.org
 [OpenCoarrays]: https://github.com/sourceryinstitute/opencoarrays