\label{sec:globalqcd}

In this section
we first present a brief historical account of PDF
determinations.
%
We then introduce the basic foundations
of the global PDF analysis program, namely the QCD factorization theorems
for lepton-hadron and hadron-hadron collisions.
%
We also discuss the scale dependence of parton distributions
as encoded in the DGLAP evolution equations.
%
In the final part of this section
we briefly address the topic of mass effects in
deep-inelastic structure functions.

\subsection{A brief history of PDF fits}\label{sec:pdffitting.history}
\input{2-pdffitting/subsec-history}

\subsection{QCD factorization in deep-inelastic scattering}\label{sec:pdffitting.DIS}
\input{2-pdffitting/subsec-dis}

\subsection{QCD factorization in hadronic collisions}\label{sec:pdffitting.had}
\input{2-pdffitting/subsec-qcdfact}

\subsection{The DGLAP evolution equations}\label{sec:pdffitting.DGLAP}
\input{2-pdffitting/subsec-dglap}

\subsection{Heavy quark structure functions}\label{sec:pdffitting.heavyq}
\input{2-pdffitting/subsec-heavyquark}

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