a)

1. Ka2? A (2. Qd1 C Kxb4 3. Qc1 Ka5 4. Qa3#)

1. ... Kc2!

1. Qd5! B Kxb4 2. Kb2 (3. Qd6+ Ka5 4. Qa3#) Ka5 3. Qxe5 Kb4 4. Qc3#

1. Qd1? C (2. Ka2 A (threat reversal in tries) Kxb4 3. Qc1 Ka5 4. Qa3#)

1. ... Kxb4! 2. Qc2? Ka3 3. Qc3 b4 4. Qb2#

2. ... Ka5!

2. Qc1? (3. Ka2 Ka5 4. Qa3#)

2. ... Kxb3!

2. Kb2? (3. Qd6+ Ka5 4. Qa3#) Ka5 3. Qa1+ Kb4 4. Qa3#

2. ... Kc5!

b)

1. Qd5? B Kxb4 2. Kb2? (3. Qd6+ Ka5 4. Qa3#) Ka5! 3. Qxe5 Kb4 4. Qc3#

3. ... Ka6!

2. Kc2? (3. Qd6+ Ka5 4. Qa3#) Ka3 3. Qxb5 Ka2 4. Qa4#

2. ... Ka5!

1. Ka2! A (characteristic twins) (2. Qd1 C Kxb4 3. Qc1 Ka5 4. Qa3#) Kc2 2. Rxb5 Kc3 3. Rd5 Kc2/b5 4. Qc7/Qc5#

2. ... Kc1 3. Rd5 (4. Qc7#)

1. Qd1? C (2. Ka2 A (threat reversal) Kxb4 3. Qc1 Ka5 4. Qa3#, 2. Qe1+ Kd3 3. Rxb5 Kd4 4. Rd5#)

1. ... Kxb4! 2. Qc2? Ka3 3. Qc3 b4 4. Qb2#

2. ... Ka5!

2. Qc1? (3. Ka2 Ka5 4. Qa3#)

2. ... Kxb3!

2. Kb2? (3. Qd6+ Ka5 4. Qa3#) Ka5 3. Qa1+ Kb4 4. Qa3#

2. ... Kc5!

Keywords: twin (characteristic), sequence reversal II (threat reversal), stalemate dissolution, flight giving key, sacrifice key (a), sacrifice of white pieces, passive sacrifice, selfblock, remote selfblock, selfpinning