add a cite section

doc/Cite.md

@@ -0,0 +1,19 @@
+  <refmeta>
+    <refentrytitle>Cite</refentrytitle>
+    <manvolnum>3</manvolnum>
+    <refmiscinfo>libvips</refmiscinfo>
+  </refmeta>
+
+  <refnamediv>
+    <refname>Cite</refname>
+    <refpurpose>References to cite for libvips</refpurpose>
+  </refnamediv>
+
+Martinez, K. and Cupitt, J. (2005) [VIPS -- a highly tuned image processing
+software architecture](http://eprints.ecs.soton.ac.uk/12371). In Proceedings
+of IEEE International Conference on Image Processing 2, pp. 574-577, Genova.
+
+Cupitt, J. and Martinez, K. (1996) [VIPS: An image processing system
+for large images](http://eprints.soton.ac.uk/252227/1/vipsspie96a.pdf),
+Proc. SPIE, vol.  2663, pp. 19--28.
+

doc/Makefile.am

@@ -147,6 +147,7 @@ markdown_content_files = \
 	Using-vipsthumbnail.md \
 	How-it-opens-files.md \
 	Examples.md \
+	Cite.md \
 	Making-image-pyramids.md
 
 # converted to xml in this dir by pandoc

doc/libvips-docs.xml.in

@@ -43,6 +43,7 @@
     <xi:include href="xml/How-it-opens-files.xml"/>
     <xi:include href="xml/Making-image-pyramids.xml"/>
     <xi:include href="xml/Using-vipsthumbnail.xml"/>
+    <xi:include href="xml/Cite.xml"/>
     <xi:include href="xml/Examples.xml"/>
   </chapter>