on page 4 of the March 17th lecture found at(adsbygoogle = window.adsbygoogle || []).push({});

http://www-math.mit.edu/~sara/tolman.lectures/

(you need to scroll down a bit to see the link the March17

lecture)

In the first corollary, when they say map 1 = map 4 = 0 do

they mean these are 0-homomorphisms?

Another other dumb question I had is about the bottom

corollary on the same page. What is it saying/what does it

mean? Where could I find a sketch of it's proof? That

might help me better understand the corollary. Or is

an accurate sketch of its proof basically be the sequence of

theorems & corollaries above it?

Thanks a lot :)

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# Exact sequence & meaning of a corollary?

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