Published in Kido (the strongest Japanese go magazine) in 1996, in the monthly problem-solving competition, problem 8 ends in a parallel double snapback ; it is hard to solve correctly, as the ko resistance looks irrefutable...
(;SZ[19]AW[no]AW[oo]AW[po]AW[mp]AW[pp]AW[mq]AW[pq]AW[qq]AW[mr]AW[ms]AW[ps]AB[nn]AB[on]AB[pn]AB[qn]AB[lo]AB[mo]AB[qo]AB[lp]AB[qp]AB[lq]AB[rq]AB[lr]AB[or]AB[rr]AB[ls]GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]RU[Japanese]KM[0.00]KK[^Bestiary^Snapback];B[np]C[The cut is the key move (but may ber played later)];W[nq]C[The cut is the key move (but may ber played later)];B[pr];W[qr]
(;B[rs]C[this move is the real key stone];W[qs]C[this move is the real key stone];B[oq];W[os];B[ns]C[a very unusual parallel double snapbackRIGHT]
(;W[nr]C[a very unusual parallel double snapback];B[ns]C[RIGHT])
(;W[op]C[a very unusual parallel double snapback];B[np]C[RIGHT]))
(;B[os]BM[1]
(;W[rs]C[this unexpected resistance ends in ko (because of the corner properties)])
(;W[qs]C[of course, if white connects.....];B[oq];W[op];B[rs];W[np];B[nr];W[ns];B[or]C[RIGHT])))