readme edit

README.md

@@ -12,7 +12,7 @@ For prior models, see the [U.S. Seismic Hazard Maps – Hawaii][3] data release.
 
 All NSHM Hawaii sources are assigned to the top-level `volcanic` tectonic setting.
 
-## References
+## Reference
 
 Petersen, M.D, Shumway, A.M., Powers, P.M., Moschetti, M.P., Llenos, A.L., Michael, A.J., Mueller,
 C.S., Frankel, A.D., Rezaeian, S., Rukstales, K.S., McNamara. D.E., Okubo, P.G., Zeng, Y., Jaiswal,