- \cite{xtremweb}. It is easy to install and maintain and it is supported by a Grid
-middleware (ARC \cite{arc}) and a workflow engine (JOpera \cite{JOpera}). It consists in
-three components: one coordinator, a set of workers and at least one
+ \cite{xtremweb}. It is easy to install, maintain, and it is supported by a Grid
+middleware (ARC \cite{arc}) and a workflow engine (JOpera \cite{JOpera}). It consists in
+three components: one coordinator, a set of workers, and at least one