Improve benchmarks readme

Author: Owen Jones

benchmarks/LIBRARIES/README.txt

@@ -22,7 +22,7 @@ of the sub-libraries:
 ---------------------------
 
 1. Install "Java OpenJDK 8" by using the standard package management system of
-   Ubuntu.
+   Ubuntu. (e.g. openjdk-8-jdk-headless)
 2. Create a directory "openjdk-8" into this directory.
 3. Locate the file "rt.jar" of "Java OpenJDK 8" on the disc. It typically
    resides at location:
@@ -48,9 +48,11 @@ Alternative installation:
 (2) Apache Tomcat 9
 -------------------
 
-1. Download Tomcat 9 from the web "http://tomcat.apache.org/download-90.cgi".
-   You can try this direct link:
-      http://mirrors.ukfast.co.uk/sites/ftp.apache.org/tomcat/tomcat-9/v9.0.0.M20/bin/apache-tomcat-9.0.0.M20.zip
+1. Download Tomcat 9 from:
+      http://tomcat.apache.org/download-90.cgi
+   Choose the core binary distribution in zip format. You can also use this
+   direct link (which may not be the most recent version):
+      http://archive.apache.org/dist/tomcat/tomcat-9/v9.0.0.M21/bin/apache-tomcat-9.0.0.M21.zip
 2. Unpack the downloaded ZIP file into this directory and rename its root
    directory to: apache-tomcat-9