I saw Yoon Young-Soon show this problem during one of her lectures at the european go congress this year. I liked it. ;-)
(;AB[pd]AB[qd]AB[re]AB[qf]AB[oe]AB[qb]AB[ne]AB[mc]AB[nc]AW[nd]AW[od]AW[oc]AW[ob]AB[nb]AW[le]AW[pe]AW[pf]AW[pg]AB[md]AW[me]AB[nf]AW[ld]AB[kc]AB[ng]AW[mh]AB[rg]AW[qg]AB[qe]AW[rh]AW[pi]AW[kd]AB[jc]AW[jd]AB[id]AW[ie]AB[hd]AW[jf]AW[ni]C[White to rescue his M15 group. :-)]AB[ib]AW[ra]AB[qa]AB[rb]AW[qc]AB[rc]AB[mg]AW[lg]AB[lh]AB[kh]AB[lj]AW[pk]AW[kg]AW[jh]AB[ji]AB[ii]AB[gf]AW[ig]AW[he]AB[hf]AB[ih]AB[gh]AB[if]AW[ge]AW[gd]AW[gc]AB[hb]AB[hc]AB[fe]AB[ed]AB[eb]AB[gb]AW[fc]AB[de]AB[fb]AB[db]AW[cb]AW[cc]AB[cd]AW[bd]AW[ac]AW[bb]AB[be]AP[goproblems]
(;W[oa]
(;B[lc]
(;W[nh]C[Well done. P19 extends the white liberties in sente after which white whins the capturing race.RIGHT])
(;W[mf]C[Well done. P19 extends the white liberties in sente after which white whins the capturing race.RIGHT])
(;W[og]C[Well done. P19 extends the white liberties in sente after which white whins the capturing race.RIGHT])
(;W[of]C[Well done. P19 extends the white liberties in sente after which white whins the capturing race.RIGHT]))
(;B[na];W[lc];B[lb];W[ma];B[mb];W[kb];B[la];W[ka]C[Good job! Normally black would have to give in to p19, but if he tries to resist he dies like this.RIGHT])
(;B[pc];W[lc];B[lb];W[mb];B[ma];W[na];B[mb];W[kb]C[If black tries to resist p19 by taking a liberty he collapses. Well done!RIGHT]))
(;W[nh];B[oa]C[White loses the capturing race!])
(;W[mf];B[oa]C[White loses the capturing race!])
(;W[og];B[oa]C[White loses the capturing race!])
(;W[of];B[oa]C[White loses the capturing race!])
(;W[na];B[lc]C[o19 does not help white since he still will lose the capuring race.])
(;W[lc];B[oa]C[White cannot capture o18, so he will die. ;-((]))