March 26 is Paul ErdÃ¶s birthday. The book about ErdÃ¶s by Paul Hoffman is a nice read and thought provoking. ErdÃ¶s’ concept of the BOOK recording the most elegant proofs is one that is natural for both mathematicians and engineers even though he might have disagreed. The relationship between mathematics and engineering is peculiar: ErdÃ¶s like many other “pure” mathematicians didn’t care about applications although his compatriot von Neumann thought otherwise. The famous number theorist GH Hardy, in his very unapologetic Apology, boasted about the inapplicability of his work – although 20 years later some of it became standard tools for cryptography.