• Joël Quenneville (Twitter)
• Elm's Universal Pattern episode
• List.concatMap is the same pattern as andThen under a different name
• andThen identity can be used to flatten something
• Dillon's Combinators article
• Martin Janiczek's elm-list-cartesian package gives two valid map2 implementions for List
• Monoid - need a way of having something empty, and way to combine two things - for example addition for numbers starting with 0
• Jeroen's elm-review-simplify package

More of Joël's distillation of category theory ideas:

• Running out of maps (applicatives)
• The Mechanics of Maybe (taking maybe apart and putting it back together)
• Two ways of looking at map functions (functors)
• Elm's universal pattern (applicatives)
• Inverting a binary tree (folding, catamorphisms)
• Joël's directory of blog posts on the ThoughtBot blog