Multiply defined labels on the user manual (pdf)

[asr]

When running make latexpdf PDFLATEX=xelatex, I got some warnings like

LaTeX Warning: Label `language/with-abstraction:ill-typed-with-abstractions' mu
ltiply defined.

These warnings are generated because the cross-references were created using

`Section title`_

instead of

:ref:`my-reference-label`

In addition, the Sphinx documentation says:

Using ref is advised over standard reStructuredText links to sections (like Section title_) because it works across files, when section headings are changed, and for all builders that support cross-references.

Please continue using :ref: instead of Section title_.