Help remembering a Putnam Problem I recall that there was a Putnam problem which went something like this:
Find all real functions satisfying
$$f(s^2+f(t)) = t+f(s)^2$$
for all $s,t \in \mathbb{R}$.
There was a cool trick to solving it that I wanted to remember. But I don't know which test it was from and google isn't much help for searching with equations.
Does anyone know which problem I am thinking of so I can look up that trick?

No idea. But I have a book called Putnam and Beyond by Gelca and Andreescu, and on page 185 they present a problem from  a book called Functional Equations: A Problem Solving Approach by B. J. Venkatachala, from Prism Books PVT Ltd., 2002. I think the Ltd. means the publisher is British.  
Almost, the publisher is (or was?) in India (Bangalore):
http://www.prismbooks.com/ 
http://www.hindbook.com/order_info.php
EDIT, December 3, 2011: The book is available, at least, from an online firm in India that is similar to Amazon.com 
http://www.flipkart.com/m/books/8172862652 
on
http://www.flipkart.com/ 
I cannot tell whether they ship outside India. But it does suggest that contacting the publisher by email is likely to work.
