Microsoft didn't just announce one Surface tablet today -- it's announced one for each of the main varieties of Windows.

ENGADGET: Microsoft announces Surface for Windows 8 Pro: Intel inside, optional pen input

Second, when the campaign began in earnest there were three main varieties of polio, each of which required a specially tailored vaccine.

ECONOMIST: Can a businessmen��s club eradicate polio from the world?

It comes in four main varieties.

ECONOMIST: Japanese finance: Rich pickings for the gaijin | The