diff --git a/docs/iris/src/userguide/citation.rst b/docs/iris/src/userguide/citation.rst
index 56eab0a4eb..f91bc670f0 100644
--- a/docs/iris/src/userguide/citation.rst
+++ b/docs/iris/src/userguide/citation.rst
@@ -48,7 +48,7 @@ For example::
 
  Iris. Met Office. git@github.com:SciTools/iris.git 06-03-2013
 
-.. _How to cite and describe software: http://software.ac.uk/so-exactly-what-software-did-you-use
+.. _How to cite and describe software: https://software.ac.uk/how-cite-software
 
 
 Reference: [Jackson]_.
diff --git a/docs/iris/src/userguide/cube_maths.rst b/docs/iris/src/userguide/cube_maths.rst
index eebff53e62..1b1b2dbe66 100644
--- a/docs/iris/src/userguide/cube_maths.rst
+++ b/docs/iris/src/userguide/cube_maths.rst
@@ -243,7 +243,7 @@ unit (if ``a`` had units ``'m2'`` then ``a ** 0.5`` would result in a cube
 with units ``'m'``).
 
 Iris inherits units from `cf_units <https://scitools.org.uk/cf-units/docs/latest/>`_
-which in turn inherits from `UDUNITS <https://www.unidata.ucar.edu/software/udunits/udunits-current/doc/udunits/udunits2.html>`_.
+which in turn inherits from `UDUNITS <https://www.unidata.ucar.edu/software/udunits/udunits-current/udunits2.html>`_.
 As well as the units UDUNITS provides, cf units also provides the units
 ``'no-unit'`` and ``'unknown'``. A unit of ``'no-unit'`` means that the
 associated data is not suitable for describing with a unit, cf units