head_dunce writes: "A bill introduced Thursday by a bipartisan group of U.S. lawmakers seeks to make it easier for states to collect sales taxes stemming from online purchases. Amazon is among the e-retailers supporting the proposal, while a lobbying group representing eBay and Overstock.com stands opposed."
We warn the reader in advance that the proof presented here depends on a
clever but highly unmotivated trick.
-- Howard Anton, "Elementary Linear Algebra"