Correct contract bridge / by E.V. Shepard ; including the official Laws of contract bridge adopted by the Whist Club, New York, and by all the leading clubs in America.

XI
OVERCALLING DOUBLES
IF you have nothing to say, when your partner's
bid is doubled at your right, say it-by passing.
If you are strong, let your partner know that by
interposing a bid before a response can be made to
the double.
A sound informatory double, like an opening notrump declaration, warns you that game hopes ordinarily must be the limit of your ambition. Unless
the very unusual nature of your hand causes a slam
possibility to shriek in your ear, do not attempt slam
bidding.
Some warnings hardly can be repeated too often.
Note the meaning of adverse bids as well as those by
partner. If an adversary announces by an opening
bid that he holds at least two sure tricks, or if he
makes an informatory-double that shows a probable
three defensive tricks, it is best to believe that he
tells the truth.
Show complete satisfaction with your partner's
doubled bid and that you expect game, by jumping
the contract to the limit of your strength, provided
that does not exceed game. The following hand
justifies jumping partner's doubled bid of i-Spade,
to 4-Spades; although Y's hand indicates fulfillment
of a contract of 5-odd such a bid is not advisable:
99