Happy Birthday, Mathman

[Peter Farrell]

I was just reminded that today is Don Cohen's birthday. His "Calculus By and For Young People" was a major influence on my approach to math. For a while after he died his site was down but now it's back up and you can download his excellent books as pdfs. 

He was a positive and encouraging soul. In fact, he was the first person to buy my book! We miss you, Don.

Peter