Please, what is a derivative of:

?

Many thanks!

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- Aug 5th 2013, 08:00 AM #1

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- Aug 5th 2013, 08:19 AM #2

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- Aug 5th 2013, 11:20 AM #3

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- Aug 6th 2013, 06:14 AM #4

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- Aug 6th 2013, 08:05 AM #5

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