diff -r b92529dc95c5 -r 90bc8cccc218 document/root.bib
--- a/document/root.bib	Sat Jan 05 00:31:43 2013 +0000
+++ b/document/root.bib	Sun Jan 06 23:50:24 2013 +0000
@@ -38,10 +38,10 @@
 }
 
 @book{Boolos87,
-  author    = {G.~Boolos and R.~C.~Jeffrey},
-  title     = {{C}omputability and {L}ogic (2.~ed.)},
+  author    = {G.~Boolos and J.~P.~Burgess and R.~C.~Jeffrey},
+  title     = {{C}omputability and {L}ogic (5th~ed.)},
   publisher = {Cambridge University Press},
-  year      = {1987}
+  year      = {2007}
 }
 
 @inproceedings{WuZhangUrban11,