(;AW[pa][pb][pc][pd][qd][qe][rf][rg][qh][sh][qi][ri][qj][qk][rk][sk][rp][qo][pp][qq][ab][bb][cb][dc][dd][de][df][cg][ch][ci][bj][bk][bl][ei][eh][fg][gg][gf][hf][if][jg][jh][ji][jj][ik][il][hl][hm][gm][fl][fk][gk][fj][hj][gi][ap][bp][cp][co][cn][cm][bn][am][ai]AB[qa][qb][qc][rb][sc][rd][re][sf][pq][qr][rq][ac][bc][cc][cd][ce][be][cf][af][bg][bh][bi][cj][ck][cl][dm][dn][do][dp][cq][bq][el][ek][ej][fm][fn][gn][hn][im][jm][jl][jk][ij][ii][ih][ig][hg][hi][gh][fh][fi][qf][qg][pg][ph][pi][pj][pk][pl][ql][rl][sl]LB[sg:a][se:b][qp:c][sd:d][gj:e][ah:f][hk:g][ag:h][aj:i][ak:j][al:k]C[
From Shimada, p32.

At right: 
======

Black at "a" (atari); White at "b" (captures 2 stones); Black takes ko at "c"

The position is now the mirror-image (colour-reversed) of the starting one.

White at "d" (atari); Black at T14 (captures 2 stones); White takes ko at "c". 

We are now back where we started.

==================

At left:
=====

B at "e" (takes ko); W at "f"; B at "g" (takes ko); W at "h" (atari); B at "i" (captures 3 stones). 

The position is now the mirror-image (colour-reversed) of the starting one.

W captures "g"; B at "j"; W captures "e"; B at "k" (atari); W at A11 (captures 3 stones).

We are now back where we started.
]SZ[19]N[from "Mathematics of Go Game" -- "Igo no suri" (Mathematical Theory of Go) -- by SHIMADA Takuya, publ 1958 by Maki Shoten.]

(;B[sg];W[se];B[qp];W[sd];B[sf];W[qq];B[sg];W[se];B[qp])
(;B[gj];W[ah];B[hk];W[ag];B[aj];W[hj];B[ak];W[gi];B[al];W[ai];B[gj]))