replace text-based reference with proper label

Author: cwehmeyer

manuscript/manuscript.tex

@@ -91,7 +91,7 @@ \subsection{Scope}
 
 In this tutorial, we assume that the reader is familiar with MD simulation and standard analysis of MD simulations of peptides and proteins, such as computation of torsion angles and distances (see Ref.~\cite{dror2012biomolecular} for a review on the MD simulation of biomolecules, and Ref.~\cite{mdtutorial} for a tutorial on MD simulations).
 
-We further assume that the reader is familiar with the basic ideas and theory underlying Markov modeling and will only give a brief reminder of the basic concepts in Section 2.
+We further assume that the reader is familiar with the basic ideas and theory underlying Markov modeling and will only give a brief reminder of the basic concepts in Section~\ref{sec:prereq}.
 
 For those seeking further resources, the recent perspective ``\emph{Markov State Models: From an Art to a Science}''~\cite{msm-brooke} provides a timeline of methods advances with relevant citations,
 while ``\emph{Markov models of molecular kinetics: Generation and validation}''~\cite{msm-jhp} describes the basic MSM theory and methodology and provides the underlying mathematics in detail.
@@ -108,6 +108,7 @@ \subsection{Scope}
 The lessons start with a showcase of the PyEMMA workflow and follow up with in-depth lessons on specific topics.
 
 \section{Prerequisites}
+\label{sec:prereq}
 
 In the following, we summarize the recommended theory and background knowledge of Markov state modeling for this tutorial.
 Then, we address the software required to work through the lessons.