Citation for the three state equations.

thesis.bib

@@ -3693,4 +3693,16 @@
   pages     = {262--277},
   publisher = {Springer},
   year      = {2005}
+}
+
+# Three state equations
+@inproceedings{Mellies14,
+  author    = {Paul{-}Andr{\'{e}} Melli{\`{e}}s},
+  title     = {Local States in String Diagrams},
+  booktitle = {{RTA-TLCA}},
+  series    = {{LNCS}},
+  volume    = {8560},
+  pages     = {334--348},
+  publisher = {Springer},
+  year      = {2014}
 }

thesis.tex

@@ -1169,7 +1169,8 @@ manipulating the state cell.
 
 The literature often presents the state monad with a fourth equation,
 which states that $\getF$ is idempotent. However, this equation is
-redundant as it is derivable from the first and third equations.
+redundant as it is derivable from the first and third
+equations~\cite{Mellies14}.
 
 We can implement a monadic variation of the $\incrEven$ function that
 uses the state monad to emulate manipulations of the state cell as