Capture-avoiding substitution.

thesis.bib

@@ -759,3 +759,13 @@
   publisher = {Indiana University},
   address = {Indianapolis, IN, USA},
 }
+
+# The original lambda calculus reference
+@InProceedings{Church32,
+  author    = {Alonzo Church},
+  title     = {A Set of Postulates for the Foundation of Logic},
+  year      = {1932},
+  booktitle = {Annals of Mathematics},
+  pages     = {346--366},
+  volume    = {33}
+}