- RubyConf 2019 - The Functional Rubyist by Joe Leo
- RubyConf 2015 - A Muggle's Guide to Tail Call Optimization in Ruby by Danny Guinther
- Object Oriented Programming vs Functional Programming - Continuous Delivery
- "O.O.P. Looks Like Functional Programming When Done Right!" - Continuous Delivery - Michael Feathers
- Functional programming - Wikipedia
- Functional Programming Paradigm - geeksforgeeks
- Functional Programming In Ruby- Ruby guides
- Functional programming in Ruby - womanonrails
- First-class function - Wikipedia
- Higher-order function - Wikipedia
- The Ultimate Guide to Blocks, Procs & Lambdas - Jesus Castello
- Closures - Mozilla
- Functional Programming in Ruby — Closures - Brandon Weaver
- Closures in Ruby - geeksforgeeks
- Ruby Blocks Simplified - Julianna Roen from Gusto
- Referential transparency - Wikipedia
- I/O in pure functions - Wikipedia
- I/O monad (Haskell) - Wikipedia
- Pure Functions and I/O - Alvin Alexander
- Immutable Enumerators with Tom Stuart