diff --git a/user-doc/Intro.txt b/user-doc/Intro.txt
index cf0b0d5c04c8300fc4e9ff27c4ecc440ca6c4ab7..0d0216f8c3b658717e59f8d32a998d027bf9f99c 100644
--- a/user-doc/Intro.txt
+++ b/user-doc/Intro.txt
@@ -4,7 +4,7 @@
 \warning This is the manual for the development version of PLUMED. It might
 contain buggy code. See this page: \ref CHANGES-UNRELEASED
 
-PLUMED is a plugin that works with a large number of molecular dynamics codes.  It can be used
+PLUMED \cite plumed1 is a plugin that works with a large number of molecular dynamics codes.  It can be used
 to analyse features of the dynamics on-the-fly or to perform a wide variety of free energy methods.
 The original PLUMED 1 was highly successful and had over 1000 users.  PLUMED 2 \cite plumed2 constitues an 
 extensive rewrite of the original in a way that makes it more modular and thus easier to implement 
diff --git a/user-doc/bibliography.bib b/user-doc/bibliography.bib
index 2f7ff66c8288c1de683cb470937b39915561c4a4..10fd9ac901b8aa11d5336f4ee163a84edf7256ff 100644
--- a/user-doc/bibliography.bib
+++ b/user-doc/bibliography.bib
@@ -1384,6 +1384,18 @@ journal = { J. Chem. Phys. }
 	Volume = {130},
 	Year = {2008}}
 
+
+@article{plumed1,
+author = {Bonomi, Massimiliano and Branduardi, Davide and Bussi, Giovanni and Camilloni, Carlo and Provasi, Davide and Raiteri, Paolo and Donadio, Davide and Marinelli, Fabrizio and Pietrucci, Fabio and Broglia, Ricardo A and Parrinello, Michele},
+title = {{PLUMED: A portable plugin for free-energy calculations with molecular dynamics}},
+journal = {Computer Physics Communications},
+year = {2009},
+volume = {180},
+number = {10},
+pages = {1961--1972}
+}
+
+
 @book{zwan+01book,
 	Address = {New York},
 	Author = {Robert Zwanzig},