message: Document dependencies for building the doc
diff: @@ -175,8 +175,8 @@ Documentation
  To build the documentation, `sphinx-doc <http://www.sphinx-doc.org>`_ and
  `sphinxcontrib-bibtex <https://sphinxcontrib-bibtex.readthedocs.io>`_ are
  required. As the documentation is auto-tested, `CGAL`_, `Eigen`_,
  -`Matplotlib`_, `NumPy`_ and `SciPy`_ are also mandatory to build the
  -documentation.
  +`Matplotlib`_, `NumPy`_, `POT`_, `Scikit-learn`_ and `SciPy`_ are
  +also mandatory to build the documentation.
  Run the following commands in a terminal:
  @@ -192,8 +192,8 @@ CGAL
  ====
  Some GUDHI modules (cf. :doc:`modules list </index>`), and few examples
  -require CGAL, a C++ library that provides easy access to efficient and
  -reliable geometric algorithms.
  +require `CGAL <https://www.cgal.org/>`_, a C++ library that provides easy
  +access to efficient and reliable geometric algorithms.
  The procedure to install this library
  