fix the docs

docs/algebra.tex

@@ -3,7 +3,7 @@
 \subsection{COFE}
 
 \begin{defn}[Chain]
-  Given some set $T$ and an indexed family $({\nequiv{n}} \subseteq T \times T)_{n \in \mathbb{N}}$ of equivalence relations, a \emph{chain} is a function $c : \mathbb{N} \to T$ such that $\All n, m. n < m \Ra c (m) \nequiv{n} c (n+1)$.
+  Given some set $T$ and an indexed family $({\nequiv{n}} \subseteq T \times T)_{n \in \mathbb{N}}$ of equivalence relations, a \emph{chain} is a function $c : \mathbb{N} \to T$ such that $\All n, m. n \leq m \Ra c (m) \nequiv{n} c (n)$.
 \end{defn}
 
 \begin{defn}