diff --git a/common/modules/metadata-challenge.org b/common/modules/metadata-challenge.org
index 3716e6c..def925a 100644
--- a/common/modules/metadata-challenge.org
+++ b/common/modules/metadata-challenge.org
@@ -1,145 +1,150 @@
 #+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
 * Explore the metadata landscape
   :PROPERTIES:
   :CUSTOM_ID: main
   :END:
 ** Preliminary questions
   :PROPERTIES:
   :CUSTOM_ID: thesourcecode
   :END:
 
 #+BEGIN_QUOTE
    “Ontologies are agreements, made in a social context, to accomplish some objectives.
   It's important to understand those objectives, and be guided by them.\"\\
      \hfill T. Gruber, The Pragmatics of Ontology, 2003
 #+END_QUOTE
 
 #+Beamer: \pause
 *** /Software Ontology/
     :PROPERTIES:
     :BEAMER_env: block
     :BEAMER_act: +-
     :END:
       + What is software ?
       + With what terms should we describe a /software artifact/?
       + What about /software source code/ ?
 
 ** The metadata challenge
 #+latex: \begin{center} \huge{What is software ?} \end{center}
 #+BEAMER: \pause
 ***  Software as a concept 				      :B_block:BMCOL:
     :PROPERTIES:
     :BEAMER_col: 0.5
     :BEAMER_env: block
     :END:
     - software project / entity
 #+BEAMER: \pause
     - the creators and the community around it
 #+BEAMER: \pause
 
 ***  Software artifact 					      :B_block:BMCOL:
     :PROPERTIES:
     :BEAMER_col: 0.5
     :BEAMER_env: block
     :END:
     - the binaries for different environments
 #+BEAMER: \pause
     - the *software source code* for each version
 
 ** This is /software/?
 #+latex: \begin{center}
 #+ATTR_LATEX: :width .38\linewidth
 file:this-is-not-a-pipe.png
 #+latex: \end{center}
 
 \hfill  What about **/software source code/** ?
 
 ** Metadata about Software Source Code
   :PROPERTIES:
   :CUSTOM_ID: softwareisdifferent
   :END:
 *** Software metadata objectives
     manage, share, discover, archive /software source code/
 #+BEAMER: \pause
 
 *** Use cases 				      :B_block:BMCOL:
     :PROPERTIES:
     :BEAMER_col:
     :BEAMER_env: block
     :END:
     - *semantic search*: find software by author, version, keywords
     - browse /source code/ with context information
     - cite and be cited
 #+BEAMER: \pause
 
 *** 							    :B_ignoreheading:
     :PROPERTIES:
     :BEAMER_env: ignoreheading
     :END:
 *** LOV- Linked open vocabularies
     \hfill /“Vocabularies provide the *semantic glue* enabling data to become *meaningful data*. ”/
 
 
 ** Where is the metadata available ?
-
+  :PROPERTIES:
+  :CUSTOM_ID: where-is-the-metadata-1
+  :END:
 *** Catalogs and registries 					    :B_block:
     :PROPERTIES:
     :BEAMER_COL: .4
     :BEAMER_env: block
     :END:
    #+ATTR_LATEX: :width \extblockscale{\linewidth}
     - libraries.io
     - OpenHub
     - OntoSoft
 
 
 *** Publisher's repositories 					    :B_block:
     :PROPERTIES:
     :BEAMER_COL: .4
     :BEAMER_env: block
     :END:
    #+ATTR_LATEX: :width \extblockscale{\linewidth}
     - GitHub
     - Bitbucket
     - SourceForge
 
 #+BEAMER: \pause
 *** advantages and drawbacks 					    :B_block:
     :PROPERTIES:
     :BEAMER_env: block
     :BEAMER_opt:
     :END:
 
       |              | registries              | repositories                   |
       |--------------+-------------------------+--------------------------------|
       | accuracy     | - not created by author | + added by authors/maintainers |
       | completeness | + very detailed         | - not a priority               |
       | longevity    | - depends on registry   | - depends on publisher         |
 
 **  Where is the metadata available ?
+  :PROPERTIES:
+  :CUSTOM_ID: where-is-the-metadata-2
+  :END:
 *** in the /software source code/ itself 			    :B_block:
     :PROPERTIES:
     :BEAMER_env: block
     :BEAMER_opt:
     :END:
   - package management file
   - CITATION file
   - .About file
   - codemeta.json file
 
 #+BEAMER: \pause
 *** advantages and drawbacks 					    :B_block:
     :PROPERTIES:
     :BEAMER_env: block
     :BEAMER_opt:
     :END:
   |              | metadata file                                         |
   |--------------+-------------------------------------------------------|
   | accuracy     | + created by author and evolves with code             |
   | completeness | - depends on the authors knowledge of metadata        |
   | longevity    | + not dependent on platform (repository or registry ) |
 
 #+BEAMER: \pause
 ***
     \hfill *Bottomline:* to insure the archival of metadata, keep it *in* the data