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Structured Q&A mental model
Google Search's calculator and unit converter
WolframAlpha
Google's mortgage calculator
Nerdwallet
Google maps
Reddit
Quora
Bing
Generic library of functions mental model
NIST Digital Library of Mathematical Functions
Special Functions Wiki
EqWorld
Wissenschaftlicher Online Calculator
https://rosettacode.org/wiki/Rosetta_Code
http://www.codecodex.com/wiki/Fibonacci_sequence
https://literateprograms.org/fibonacci_numbers__javascript_.html
Code editors/IDEs
https://www.jqueryscript.net/blog/best-json-viewer.html