  In \cite{J} M. Jara has presented a method, reducing the proof of the
hydrodynamic limit of symmetric exclusion processes to an homogenization
problem, as unified approach to recent works on the field as \cite{N},
\cite{F1}, \cite{F2} and \cite{FJL}. Although not stated in \cite{J}, the
reduction of the hydrodynamic limit to an homogenization problem was already
obtained (in a different way) in \cite{N}, \cite{F1}. This alternative and very
simple relation between the two problems goes back to an idea of K.\ Nagy
\cite{N}, is stated in \cite{F1}[Section B] for exclusion processes on $\bbZ^d$
and, as stressed in \cite{F2}, is completely general. The above relation has
been applied to \cite{N}, \cite{F1}, \cite{F2} and \cite{FJL} and could be
applied to other symmetric exclusion processes, mentioned in \cite{J}. In this
short note we briefly recall this unified approach in a complete general
setting. Finally, we recall how the homogenization problem has been solved in
the above previous works.
