fix typo

specifications/README.md

@@ -6,7 +6,7 @@ real-time platform-level wargaming across multiple host computers and is used wo
 especially by military organizations but also by other agencies such as those involved in
 space exploration and medicine.*
 * Wikipedia: [Distributed Interactive Simulation (DIS)](https://en.wikipedia.org/wiki/Distributed_Interactive_Simulation) IEEE Standard and [RPR FOM](https://en.wikipedia.org/wiki/RPR_FOM)
-* [Simulation Interoperabilty Standards Organization (SISO)](https://www.sisostds.org): "Simulation Interoperability and Reuse through Standards"
+* [Simulation Interoperability Standards Organization (SISO)](https://www.sisostds.org): "Simulation Interoperability and Reuse through Standards"
 * SISO [DIS / RPR FOM PSG - Distributed Interactive Simulation / Real-time Platform Reference Federation Object Model](https://www.sisostds.org/StandardsActivities/SupportGroups/DISRPRFOMPSG.aspx) Product Support Group (PSG)
 
 ## Working-Group Resources