Yesterday! Math was such an easy game to play

For the review on December 8, 2017 on Integral Theorems:

Vector fields! 
All my troubles seemed so far away
Now it looks as though they are here to stay
Oh, I believe in yesterday

Greens theorem
I'm not half the man I used to be
There's a shadow hanging over me
Green's theorem, came suddenly

Why Stokes had to come
I don't know, he wouldn't say
I must have said something wrong
Now I long for yesterday

Math was such an easy game to play
Now I need a place to hide away
Oh, I believe in yesterday!
Here is the performance of Christelle Berthon from 2008. And here is Paul Mc Cartney live in 1965 and the beatles in Munich.