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A few of us over on MITx have noticed that $\int f(x) dx $ is appearing as $\int dx f(x)$.

It's not the maths of it that worries me. It's just I recently read a justification (analytical?) of the second form somewhere but can't recall it or where I saw it.

Can anyone give me a reference?

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    Thanks, t.b. and joriki. I'd turned up these posts, but neither of them or their answers give a rationale for preferring one version or another, and that's what I'm after.2012-06-21

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The second form sometimes makes it easier for the reader to match variables of integrations with their limits. Compare $ \int_0^1\int_{-\infty}^{\infty}\int_{-\eta}^{\eta}\int_{0}^{|t|} \Big\{\text{some long and complicated formula here}\Big\}\,ds\,dt\,d\zeta\,d\eta $ and $ \int_0^1 d\eta\int_{-\infty}^{\infty}d\zeta\int_{-\eta}^{\eta}dt\int_{0}^{|t|} ds\,\Big\{\text{some long and complicated formula here}\Big\} $

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    It certainly makes things clearer. It's just I seem to remember a more "mathematical" explanation.2012-06-21