Put tile compression reference in

Author: timj

acfits.tex

@@ -1532,7 +1532,8 @@ \subsection{Lesson 4. Conventions are not standards}
 and for supporting hierarchical headers (\texttt{HIERARCH} and
 \emph{record-valued}) but the standard does not have anything to say
 as to which convention is preferred. Tile compression is rightfully
-thought of as a success for FITS but again tile compression is a
+thought of as a success for FITS but again tile compression
+\citep[e.g.][]{2007ASPC..376..483S,2009PASP..121..414P} is a
 convention and not a standard with no guarantee that a particular
 reader will be able to understand the compression scheme.