Update README.

README.md

@@ -5,7 +5,7 @@ Files from the [Purdue Reactive Molecular Dynamics](https://www.cs.purdue.edu/pu
 ## Relevant Papers
 
 Roughly by target platform
-- [Single core](https://www.cs.purdue.edu/puremd/docs/80859.pdf) (serial)
-- [Distributed memory](https://www.cs.purdue.edu/puremd/docs/Parallel-Reactive-Molecular-Dynamics.pdf) (message passing interface)
-- [Massively multithreaded](http://dx.doi.org/10.1016/j.jcp.2014.04.035) (single GPU)
-- [Massively multithreaded](https://www.cs.purdue.edu/puremd/docs/pgpuremd.pdf) (multi-GPU)
+- [Serial](https://www.cs.purdue.edu/puremd/docs/80859.pdf)
+- [MPI (message passing interface)](https://www.cs.purdue.edu/puremd/docs/Parallel-Reactive-Molecular-Dynamics.pdf)
+- [CUDA (single GPU)](http://dx.doi.org/10.1016/j.jcp.2014.04.035) (single GPU)
+- [CUDA+MPI (multi-GPU)](https://www.cs.purdue.edu/puremd/docs/pgpuremd.pdf)