Q: What's the contour integral around Western Europe?
A: Zero, because all the Poles are in Eastern Europe!

Addendum: Actually, there ARE some Poles in Western Europe, but they
are removable!

Q: An English mathematician (I forgot who) was asked by his
very religious colleague: Do you believe in one God?
A: Yes, up to isomorphism!

Q: What is a compact city?
A: It's a city that can be guarded by finitely many near-sighted
policemen!
-- Peter Lax