\documentclass[12pt]{report}
\usepackage[utf8x]{inputenc}

%Warning: tipa declares many non-standard macros used by utf8x to
%interpret utf8 characters but extra packages might have to be added
%such as "textgreek" for Greek letters not already in tipa
%or "stmaryrd" for mathematical symbols.
%Utf8 codes missing a LaTeX interpretation can be defined by using
%\DeclareUnicodeCharacter{code}{interpretation}.
%Use coqdoc's option -p to add new packages or declarations.
\usepackage{tipa}

\usepackage[T1]{fontenc}
\usepackage{fullpage}
\usepackage{coqdoc}
\usepackage{amsmath,amssymb}
\usepackage{url}
\begin{document}
\coqlibrary{Coqdoc.binder}{Library }{Coqdoc.binder}

\begin{coqdoccode}
\end{coqdoccode}
Link binders 
\begin{coqdoccode}
\coqdocemptyline
\coqdocnoindent
\coqdockw{Definition} \coqdef{Coqdoc.binder.foo}{foo}{\coqdocdefinition{foo}} \coqdef{Coqdoc.binder.alpha:1}{alpha}{\coqdocbinder{alpha}} \coqdef{Coqdoc.binder.beta:2}{beta}{\coqdocbinder{beta}} := \coqref{Coqdoc.binder.alpha:1}{\coqdocvariable{alpha}} \coqexternalref{::nat scope:x '+' x}{http://coq.inria.fr/stdlib/Coq.Init.Peano}{\coqdocnotation{+}} \coqref{Coqdoc.binder.beta:2}{\coqdocvariable{beta}}.\coqdoceol
\end{coqdoccode}
\end{document}