The Telegraph – 12 Ene 1990
The simplest application of suit preference occurs when a defender is leading a suit he expects his partner to ruff. In that circumstance, leading a high-ranking card asks partner to return the higher-ranking suit for communication purposes; leading a low-ranking card suggests that the lower-ranking suit will provide the needed entry for another ruff. But there are other applications of the basic concept.
Vulnerable East-West Dealer: South
Opening lead: 
K
Against two hearts, West led the king of diamonds. When East played the deuce, West next led the club ace. East played the eight and declarer followed with the queen. West played another club, dummy’s jack won the trick, and East followed with the 10. Now came the 10 of hearts from dummy, and West won the king. Just in case his partner had started with a singleton diamond, West now plunked down the diamond ace. East played the eight as South followed with the queen.
Having read somewhere that it is dangerous to lead away from a jack, West now continued with a third diamond. South drew trumps and gave up a spade, making two hearts. Of course West’s defense cannot easily be excused, but the point of the deal is that there are ways for a defender to suggest holding a particular important card, and every play East made in clubs and diamonds cried out: “Partner! Wake up! Of course I have the ace of spades.”
Thus today’s lesson: Do your sleeping in the bedroom, not at the bridge table.