Notes on Converting A&A Keywords List
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Frederic Hessmen provided an xml representation of the file which
contained equivalences to ucds.

Norman added the hierarchy to the file by creating the categories as
concepts.

Alasdair identified that some concepts were missing and added them.
- Stars: oscillations
- Galaxies: active
- Galaxies: clusters: individual: ...
- Galaxies: star clusters

Alasdair has added the collections to the file.
- Astronomical instrumentation, methods and techniques: space vehicles
  I was unsure what to do with this one. I have added a collection
  which has itself as a concept.
- Astronomical data bases: miscellaneous
  Issue about how to interpret this. I have left it as a concept
  rather than a collection.
- The Sun
  For now, I have added a collection between the general concept 'The
  Sun' and the concepts 'Sun: xxx'.
- Planets: rings
  I have left this unchanged.
  Should it be part of Planets and Satellites?
- Stars
  Handled in the same way as 'The Sun'
- Stars: Binaries (including multiple)
  I have added this to the collection 'Stars: Binaries'.
- Stars: Planetary Systems
  I have added this to a collection of the same name.
- The Galaxy
  Handled in the same way as 'The Sun'
- Galaxies
  Handled in the same way as 'The Sun'