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What Is Mathematics?

Richard Courant and Herbert Robbins

Recommended by 1 person on the record.

The bar next to each date shows how long ago it was said: 7d is days, 4yr is years.

This book on rcmnd →

That little bar

It says how long ago something was said, so you can tell last month from 2014 without doing the arithmetic. Full and green is recent; it drains and cools as the date gets older, and empties completely at about 6 years.

A striped bar means the date itself is an estimate — the source did not carry an exact one. An entry with no date at all gets no bar.