(;
AB[dr][eq][dp][cp][bp]
AW[co][do][eo][ep][cm][cj]
C[White plays.

Source:
    The Endgame, Chap. 5, pp. 99-100
    Tomoko Ogawa & James Davies, Ishi Press]
(;
W[bo]
C[In the pressure of a game, White can easily make this mistake of simply blocking!];
B[ao]
C[Black simply has to hane here in sente.];
W[an];B[ap];W[bn]
C[White ends in gote, and Black maximizes his corner territory.  But White has something MUCH better.]
)
    (;
    W[ao]
    C[Correct.  This move is well worth memorizing!];
    B[bo];W[bn]
    (;
    B[ap]
    C[If Black descends here, White can take sente to play elsewhere.  Black cannot push through up the left side.]
    )
        (;
        B[]
        C[So Black will play elsewhere.];
        W[ap]
        C[Later, the sente push here will be White's privilege.];
        B[aq]
        C[Black has to block here.];
        W[an];B[bq]
        C[White has taken 2 points from Black's corner in sente.]
        )
    )
)

