diff --git a/common/modules/foss-commons.org b/common/modules/foss-commons.org
index 13b4e56..9b6fa40 100644
--- a/common/modules/foss-commons.org
+++ b/common/modules/foss-commons.org
@@ -1,64 +1,67 @@
 #+COLUMNS: %40ITEM %10BEAMER_env(Env) %9BEAMER_envargs(Env Args) %10BEAMER_act(Act) %4BEAMER_col(Col) %10BEAMER_extra(Extra) %8BEAMER_opt(Opt)
 #+INCLUDE: "prelude.org" :minlevel 1
 * The Free Software Commons
   :PROPERTIES:
   :CUSTOM_ID: main
   :END:
 ** Free Software
 *** Definition (Free Software)
     A program is *free software* if the program's users have the four
     /essential freedoms/:
     - Freedom #0, to *run* the program, for any purpose
     - Freedom #1, to *study* how the program works, and change it
     - Freedom #2, to *redistribute* copies
     - Freedom #3, to *improve* the program, and *release* improvements
 *** 							    :B_ignoreheading:
     :PROPERTIES:
     :BEAMER_env: ignoreheading
     :BEAMER_ref:
     :END:
     Free Software also comes with *obligations*, which vary according to the
     license: BSD, GPL, Apache, AGPL, . . .
 ** Why bother?
    Why, as computer scientists/teachers/students, should we bother about
    Free/Open Source Software (FOSS)?
    #+BEAMER: \pause \vfill
    FOSS has /radically changed/ the way software is:
    - developed
    - tested
    - proven
    - conceived
    - marketed
    - sold
    - maintained
    - taught
    - deployed
    - ...
 ** The Commons and FOSS
+   :PROPERTIES:
+   :CUSTOM_ID: commonsdef
+   :END:
 *** Definition (Commons)
     The *commons* is the cultural and natural resources accessible to all
     members of a society, including natural materials such as air, water, and a
     habitable earth. These resources are held in common, not owned privately.
     #+BEAMER: {\tiny\url{https://en.wikipedia.org/wiki/Commons}}
 *** Definition (Software Commons)
     The *software commons* consists of all computer software which is available
     at little or no cost and which can be altered and reused with few
     restrictions. Thus /all open source software and all free software are part
     of the [software] commons/. [...]
     #+BEAMER: {\tiny\url{https://en.wikipedia.org/wiki/Software_Commons}}
 ** But /where/ is this commons?
    #+latex: \begin{flushleft}
    #+ATTR_LATEX: :width \extblockscale{.5\linewidth}
    file:myriadsources.png
    #+latex: \end{flushleft}
    #+BEAMER: \pause
 *** Fashion victims
     - many disparate development platforms
     - a myriad places where distribution may happen
     - projects tend to migrate from one place to the other over time
     #+BEAMER: \pause
 *** One place to bind them... 					    :B_block:
     :PROPERTIES:
     :BEAMER_env: block
     :END:
     \hfill ... where can we find, track and search /all/ source code?