(;
AB[cb][eb][gb][gc][gd][ob][pb][dc][mc][pc][ed][ee][jd][qd][rd][re][qf][qg][cg][dh][eh][hh][ei][dj][hj][pj][qj][el][gm][qm][bn][rn][co][ho][io][jo][ko][no][oo][gp][op][oq][or][bq][fq][hq][lq][nq][cr]
AW[hb][nb][cc][cd][fc][ic][id][lc][ld][oc][od][de][df][ne][pe][qe][ef][gf][rf][bg][ch][ci][bi][di][qi][bm][cm][fn][gn][hn][in][jn][nn][on][pn][do][go][mo][mp][qo][ro][ep][fp][np][dq][dr][qq][pr]
PL[W]
C[White's follow-up to the marked exchange?

Source:
Go World #25, pp. 36-37
White:  Hashimoto Shoji 9P
Black:  Otake Hideo 9P
Commentary:  Kata Masao 9P]
TR[qi][qj]
(;
W[pi]
C[In the game, White misses a chance by pushing up.];
B[rj]
C[Black takes the vital point.];
W[oi]
C[After White runs out, ...];
B[rh]
C[Black crosses under to connect all the right side stones.  White has accomplished little.]
)
    (;
    W[rj]
    C[Instead, White should hane here to take advantage of the local aji.];
    B[rk];W[rg]
    C[Now White has this crawling tesuji.]
    (;
    B[rh];W[ri];B[sf];W[qk]
    C[Sacrificing 2 stones gives White this severe cut.]
    (;
    B[rl];W[pl]
    C[This kosumi destroys Black's lower right side.]
    )
        (;
        B[pk]
        C[If Black gives way with this atari, ...];
        W[ql];B[pl];W[rl];B[pm];W[qh];B[sg];W[oh]
        C[Black saves the lower right stones, but White has still devastated the side, while attacking Black's eyeless group.]
        )
    )
        (;
        B[ph]
        C[Black's other option is to try to capture White outright.];
        W[pi];B[oi];W[qh]
        (;
        B[pg];W[rh]
        (;
        B[si];W[oh]
        C[This cut set up another reading problem.  What happens?];
        B[og];W[nh];B[ng];W[mg]
        C[Black is one move short.]
        )
            (;
            B[oh]
            C[If Black safely connects, ...];
            W[si]
            C[... White's invasion is still a success, because Black owes another move to ensure life of the right side group.]
            )
        )
            (;
            B[og]
            C[Another possibility, but ...];
            W[rh];B[si];W[oj];B[ni];W[ok]
            C[... White's extension is very difficult to handle.];
            B[ri]
            C[Black can now win the semeai, but ...];
            W[pg]
            C[... White has an enduring instructive squeeze sequence.];
            B[pf];W[of];B[pg];W[ng];B[oh];W[mj];B[mi];W[li];B[mh];W[qk];B[sj];W[pk];B[rj];W[rl];B[sf];W[sl]
            C[And White captures the 2 stones below in sente.];
            B[sg];W[lj]
            C[Finally, connecting here gives White a good result.];
            B[ql]
            C[Note that cutting here doesn't work.];
            W[sn]
            C[White connects.]
            )
        )
    )
)

