duplicators.
-![Szabolcsi's analysis of *himself* as the duplicator combinator](szabolcsi-reflexive.png)
+![Szabolcsi's analysis of *himself* as the duplicator combinator](szabolcsi-reflexive.jpg)
These systems are Turing complete. In other words: every computation we know how to describe can be represented in a logical system consisting of only a single primitive operation!