Gokyo Shumyo, Section 1, Problem 72 / Solution

Continuation  

White lives in seki because Black can at most almost fill her eye space with a bent four.

Variation  

As you can see: and points are miai.

Failure at  

There is death in the hane : The door group is dead.

Failure at  

If White answers the marked stone ( in the Main Line) with here, Black kills with by making miai of a and b.