Add snippets to select references

[jaybee84]

Purpose

partially closes #234

Directions for reviewers

Are there other papers we should add to this?

Which areas should receive a particularly close look?

Is there anything that you want to discuss further?

Is the description sufficient?

Is the pull request ready for review?

Yes

Manuscript checklist

Unless otherwise noted above, this PR will be considered ready for review when all four items have been checked.

• [ ] All changes to text follow "one sentence per line" [Manubot instructions]
• [ ] All citations follow the Manubot citation instructions
• [ ] All changes or additions to tables follow the Manubot table instructions
• [ ] All figures follow the Manubot figure instructions
• [ ] All terms that need to be added to glossary have been added to #50
• [ ] There are no new spelling errors identified by the Manubot spellchecker

[AppVeyorBot]

AppVeyor build 1.0.685 for commit 4e460e99c9275f0676a3d0007bf40057029a8a7b is now complete.

Found 13 potential spelling error(s). Preview:

content/03.combining-datasets.md:7:hoc content/03.combining-datasets.md:13:ontologies content/05.model-complexity.md:31:ALS content/05.model-complexity.md:31:amyotrophic content/09. ethics_declaration.md:3:Tempus content/11. author_contributions.md:3:ICMJE content/11. author_contributions.md:5:curation content/13. figure_legends.md:3:Barplot content/14. box_1_MLtasks.md:21:subtyping content/14. box_1_MLtasks.md:23:heterog...

The rendered manuscript from this build is temporarily available for download at:

• manuscript-1.0.685-4e460e9.html
  • manuscript-1.0.685-4e460e9.pdf
  • spelling-errors-1.0.685-4e460e9.txt
  • spelling-error-locations-1.0.685-4e460e9.txt

[AppVeyorBot]

AppVeyor build 1.0.686 for commit 051c05cbb58b49f562e7dabe1e6d932821dadf56 is now complete.

Found 13 potential spelling error(s). Preview:

content/03.combining-datasets.md:7:hoc content/03.combining-datasets.md:13:ontologies content/05.model-complexity.md:31:ALS content/05.model-complexity.md:31:amyotrophic content/09. ethics_declaration.md:3:Tempus content/11. author_contributions.md:3:ICMJE content/11. author_contributions.md:5:curation content/13. figure_legends.md:3:Barplot content/14. box_1_MLtasks.md:21:subtyping content/14. box_1_MLtasks.md:23:heterog...

The rendered manuscript from this build is temporarily available for download at:

• manuscript-1.0.686-051c05c.html
  • manuscript-1.0.686-051c05c.pdf
  • spelling-errors-1.0.686-051c05c.txt
  • spelling-error-locations-1.0.686-051c05c.txt