additional links for SISO enumerations references

specifications/README.md

@@ -68,9 +68,11 @@ Guidelines are established for the verification, validation, and accreditation (
 
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-**5. SISO-REF-010-2019: Reference for Enumerations for Simulation Interoperability** <img src="SisoLogo.jpg" width="314" align="right"/>
-* https://www.sisostds.org/ProductsPublications/ReferenceDocuments.aspx
+**5. SISO-REF-010-2020: Reference for Enumerations for Simulation Interoperability** <img src="SisoLogo.jpg" width="314" align="right"/>
+* https://www.sisostds.org/ProductsPublications/ReferenceDocuments.aspx (scroll down to bottom of page)
 * *Abstract.* 
 SISO-REF-010 specifies numerical values and associated definitions for fields that are identified as enumerations in SISO Standards Products and SISO-sponsored standards published by IEEE for High Level Architecture (HLA) and Distributed Interactive Simulation (DIS). Enumerations for simulations may be applied in other architectures, such as the Test and Training Enabling Architecture (TENA).
-
+* Resources: [SISO-REF-010-2020 distribution](https://www.sisostds.org/DigitalLibrary.aspx?Command=Core_Download&EntryId=51787),
+[enumerations PDF](https://www.sisostds.org/DigitalLibrary.aspx?Command=Core_Download&EntryId=46172) and 
+[Operations Manual (OPMAN)](https://www.sisostds.org/DigitalLibrary.aspx?Command=Core_Download&EntryId=47284)
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