(;
AB[bc][cd][ce][af][bf][cf][dg][eg][bi][di][dj]
AW[bb][cb][dc][fc][de][df][ff][ag][bg][cg][ch][bk][cl]
C[White plays.

Source:
    Problem #122 from the yose volume of Gokyo Seimyo, a nearly 200 year old problem set.]
(;
W[ci]
C[A classic mistake of needlessly reducing liberties.];
B[cj]
(;
W[aj];B[bj];W[ai]
C[White seems to have made a connection, but ...];
B[ah];W[bh];B[dh]
TR[ci][cj]
C[... Black can capture the stones in a liberty shortage, because of the marked exchange.]
)
    (;
    W[bj]
    C[Again, White seems to have made a connection, but ...];
    B[ah]
    C[... Black has this diagonal tesuji to capture White's stones.]
    )
)
    (;
    W[aj]
    C[Correct.  White can now connect to the stones above.];
    B[ai]
    C[Without having any liberty shortage tricks, blocking here is Black's toughest defense, but ...];
    W[ci];B[cj];W[bj]
    TR[ag][bg][cg][ch][ci]
    C[... White's marked stones are alive in seki.  But the situation is even worse for Black.  Because the Black stones above have only 1 eye, those stones are dead.]
    )
)

