Add another relevant reference

Author: rhornung67

docs/13_rajaperf/rajaperf.rst

@@ -735,3 +735,5 @@ Other helpful references include:
   * Olga Pearce, Jason Burmark, Rich Hornung, Befikir Bogale, Ian Lumsden, Michael McKinsey, Dewi Yokelson, David Boehme, Stephanie Brink, Michela Taufer, Tom Scogland, "RAJA Performance Suite: Performance Portability Analysis with Caliper and Thicket", in 2024 IEEE/ACM International Workshop on Performance, Portability and Productivity in HPC (P3HPC) at the International Conference on High Performance Computing, Network, Storage, and Analysis (SC-W 2024). [Download here](https://dl.acm.org/doi/pdf/10.1109/SCW63240.2024.00162)
 
   * D. A. Beckingsale, J. Burmark, R. Hornung, H. Jones, W. Killian, A. J. Kunen, O. Pearce, P. Robinson, B. S. Ryujin, T. R. W. Scogland, "RAJA: Portable Performance for Large-Scale Scientific Applications", 2019 IEEE/ACM International Workshop on Performance, Portability and Productivity in HPC (P3HPC). [Download here](https://conferences.computer.org/sc19w/2019/#!/toc/14) 
+
+  * Arturo Vargas, Thomas M. Stitt, Kenneth Weiss, Vladimir Z. Tomov, Jean-Sylvain Camier, Tzanio Kolev, Robert N. Rieben, "Matrix-free Approaches for GPU Acceleration of a High-order Finite Element Hydrodynamic Application using MFEM, Umpire, and RAJA", International Journal of High Performance Computing Applications. 36(4):492-509 (2022). [Download here](https://journals.sagepub.com/doi/10.1177/10943420221100262)