UNIX spec link.

Author: janpgit

docs/index.html

@@ -56,6 +56,7 @@ <h2>Contents</h2>
 <a href="#consultations">Consultations</a><br>
 <a href="#contact">Contact</a><br>
 <a href="#schedule">Schedule</a>
+<a href="#references">References</a>
 
 <!--
 <h2><font color="red">News</font></a></h2>
@@ -156,6 +157,11 @@ <h2><a name="practices">Practices and class assignments</a></h2>
 <p>Is in the <a href="http://www.mff.cuni.cz/vnitro/is/sis/">information
 system.</a>
 
+<a name="references"><h2>References</h2></a>
+
+<p>The <a href="https://pubs.opengroup.org/onlinepubs/9699919799/">UNIX spec</a>
+(The Open Group Base Specifications Issue 7, 2018 edition).
+
 <p></p>
 <hr>
 Last changed: