The Unknown Derek Oldbury COLUMN NUMBER 20 Problem Number 20: By Ken Marriott   Black to move and draw A handy crossboard position Solution To Problem Number 19:  12-16; 19-12 14-10; 28-19 3-7 (sacrifice de-luxe); 2-11 17-14; 12-3 6-1; 15-6 9-2; 18-9 2-7 (climax); 3-10 1-5; 25-18 5-14. White wins. If you solved this one, then you really can play draughts. Game Number 20. 'Cross' Opening Sam Cohen, the world champion, contributes the following game which he played recently in a lightning handicap tournament. Black: Sam Cohen; White: S. Leschinsky. Set black men on squares 1 to 12; white men on squares 21 to 32. Start moving: 11-15 23-18; 12-16 (a balloted opening favouring White, because the single corner is weakened by this early exchange) 8-11; 8-15 24-19 (eases the situation for Black, and it is interesting to see how the master takes the initiative after this point); 16-23 27-11; 7-16 28-24; 16-19 (always a key square in defence) 24-15; 10-19 21-17; 4-8 17-14; 9-18 22-15; 5-9 25-22; 9-14 (flawless development) 29-25; 3-7 31-27; 7-11 32-28; 11-18 22-15; 2-7 25-22 Forms Diagram: Black to move   Continue: 14-18 30-25; 7-11 22-17; 11-16 17-14; 8-12 26-22; 19-23 15-11; 23-32 22-15; 32-27 14-10; 27-23 11-7; 6-9 15-11. Drawn. A good game.