diff --git a/virtual_machines/README.md b/virtual_machines/README.md
index 641affb..5db407a 100644
--- a/virtual_machines/README.md
+++ b/virtual_machines/README.md
@@ -1,2 +1,5 @@
 * [One VM to Rule Them All](http://lafo.ssw.uni-linz.ac.at/papers/2013_Onward_OneVMToRuleThemAll.pdf)
     - This is an exciting VM implementation that incorporates AST node rewriting and an optimizing compiler. It enables the implementation of, and excellent performance for, a wide range of languages.
+* [A Comparison of Software and Hardware Techniques for x86
+  Virtualization](http://www.vmware.com/pdf/asplos235_adams.pdf)
+    - virtualization theory background