(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2] RU[Japanese]SZ[19]KM[0.00] PW[me]PB[also me]AW[ea][ra][eb][ob][pb][qb][bc][cc][dc][mc][nc][ld][od][qd][sd][qe][se][qf][qg][ph][rh][ri][cm][em][bn][cn][fn][ho][dq][eq][hq][qq][br][cr][dr][er][hr][nr][or][pr][qr][rr][es]AB[bb][cb][db][fb][nb][rb][oc][pc][qc][rc][rd][re][rf][rg][sh][bl][cl][dl][bm][qo][cp][dp][ep][fp][qp][cq][fq][mq][nq][oq][pq][rq][fr][mr][ds][fs]LB[ed:1][nf:4][gl:3][oo:2]C[Cho Chickun's encyclopedia of life and death: Volume 3 Problems 1-4 Black to play I will try to figure them out in my head before putting any variations on the board (which is something I do too much when reviewing games I thinks...)] (;B[ec] ;W[fc] ;B[ed] ;W[gb] ;B[da] ;W[fa] (;B[ce] ;W[be] ;B[bd] ;W[cd] ;B[ac] ;W[ad] ;B[ab] ;W[de] ;B[cf] ;W[dd] ;B[ba]C[Seems like a pretty crude variation, black can do better]) (;B[ab] (;W[ba] ;B[bd] ;W[cd] ;B[ce] ;W[be] ;B[ac] ;W[ad] ;B[dd] ;W[bd] ;B[bf]C[so white cannot play B19 without protecting on the outside first]) (;W[ce] ;B[ba]C[probably the best for black, still aji on the outside for black epending on the situation of course]))) (;B[oa] (;W[mb] ;B[qa] ;W[na] (;B[sa] ;W[sc] ;B[sg]C[Seki, not bad for black]) (;B[sc] ;W[sa] ;B[sb] ;W[ra]C[not good enough black just dies])) (;W[qa]C[white's best refutation, black is dead] ;B[sb])) (;B[sr] ;W[rp] ;B[sp] (;W[sq]) (;W[ro] ;B[rn] ;W[sq]C[ko seems to be the only way])) (;B[ap]C[One of these four I found hardest, actually it's not so tricky once you find this move though!] (;W[ao] (;B[ar] ;W[bp] ;B[bq] ;W[aq]C[ko]) (;B[bo] ;W[an] ;B[ar] ;W[bq] ;B[bp] ;W[aq] ;B[bs] ;W[as]C[ko again])) (;W[aq] (;B[an] ;W[bp] ;B[ao] ;W[bo] ;B[am] ;W[bq]C[black is dead]) (;B[ar] (;W[bq] ;B[bp] (;W[as] ;B[an]) (;W[an] ;B[bs] ;W[as])) (;W[as] ;B[bq] ;W[ar] ;B[cs] ;W[bs] ;B[cs] ;W[ds] ;B[cs])))) (;B[qa] ;W[pa] ;B[sa] ;W[sb] ;B[sc] ;W[mb] ;B[sa] ;W[na] ;B[qa]C[ko, the only way for black]))